Campus Alert Archive
Princeton

Bomb threat against four landmark buildings; all cleared within about two hours

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NJbomb threatemergency notificationhigh confidence
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Confirmed HoaxDetermined to be a hoax. The institutional response is documented because it reveals how the alert system performed under a perceived real threat.

A caller claimed to have placed improvised explosive devices in four of Princeton's most prominent buildings: Firestone Library, Nassau Hall, the University Chapel, and the Art Museum. The Department of Public Safety issued a TigerAlert at 11:11 a.m. EDT on September 19, 2020 ordering evacuations, and all buildings were cleared within approximately two hours.

Alerts
2
Response
—
Killed
—
Injured
—
Institution
Princeton University
Private R1 · NJ
All Princeton cases →
~8,623 studentsTigerAlert
Official alert policy
Read when and how Princeton says it will use TigerAlert (formerly PTENS): summarized, quoted, and analyzed.
Documented Timeline

Alert Sequence

2 messages in sequence · 2 verified verbatim

INITIAL ALERTSMS
Verified verbatimThe Daily Princetonian: TigerAlert quoted verbatim415 chars
This is NOT a test. A bomb threat was received for the Art Museum, Firestone Library, Nassau Hall and the Chapel. The Department of Public Safety has issued an evacuation order for these buildings. Please collect your personal items including your car keys. Leave your door unlocked and open to allow the area to be inspected. Calmly leave the building and go to your building's designated evacuation assembly area.
Sent at 11:11 a.m. EDT on September 19, 2020 (a Saturday); the campus was operating under COVID-19 restrictions
The four targeted buildings are among Princeton's most iconic structures: Nassau Hall (1756) houses the university president's office, Firestone Library is the main research library, and the Chapel is one of the largest university chapels in the world
The instruction to leave doors unlocked and open is standard procedure to facilitate bomb squad inspections
ALL CLEARSMS+1h 54m
Verified verbatimPlanet Princeton quoting the verbatim TigerAlert all-clear text sent at 1:05 PM EDT on September 19, 2020, corroborated by The Daily Princetonian132 chars
Public Safety has confirmed there is no threat and has issued an ALL CLEAR related to the bomb threat. Normal activities can resume.
Sent at 1:05 PM EDT on September 19, 2020, after sweeps of all four buildings by law enforcement confirmed no explosive devices
The phrasing 'Public Safety has confirmed there is no threat and has issued an ALL CLEAR' is the institutional attribution form -- crediting DPS rather than asserting the all-clear from the alert system itself
Princeton's campus was operating at reduced capacity during the fall 2020 semester due to COVID-19 restrictions, meaning fewer people were physically present in the targeted buildings
Message elements

How the first alert is built

To check this alert, Claude (an AI) read it in full 25 separate times, independently. Each read decided whether the message answers each of the six questions and gave a short reason. A final reviewer then weighed all 25 and wrote the plain-English verdict you see when you open a row. The score (for example 22/25) is how many reads agreed; the 25 individual reads are tucked underneath if you want to check them.

This is NOT a test. A bomb threat was received for the Art Museum, Firestone Library, Nassau Hall and the Chapel. The Department of Public Safety has issued an evacuation order for these buildings. Please collect your personal items including your car keys. Leave your door unlocked and open to allow the area to be inspected. Calmly leave the building and go to your building's designated evacuation assembly area.

  • Sourcepresent25/25

    Final assessment

    Unanimous that the source is present; the alert names the Department of Public Safety as the issuing authority.

    Who is sending the alert and who is responding. People act faster on a message from a clearly identifiable, credible sender, such as a named department, the police, or a branded alert system, than on an anonymous notice. A branded signature counts.

    See all 25 individual reads
    1. present: It names "The Department of Public Safety", identifying the source.
    2. present: It names "The Department of Public Safety", the issuing authority.
    3. present: It names "The Department of Public Safety", the issuing authority.
    4. present: It names "The Department of Public Safety" as the issuing authority.
    5. present: It names "The Department of Public Safety", the issuing authority.
    6. present: It names "The Department of Public Safety", the issuing authority.
    7. present: "The Department of Public Safety" is named as the issuing authority.
    8. present: It names "The Department of Public Safety", an issuing authority.
    9. present: It names "The Department of Public Safety", the issuing authority.
    10. present: It names "The Department of Public Safety", the issuing authority.
    11. present: It names "The Department of Public Safety" as the issuing authority.
    12. present: "The Department of Public Safety" is named as the issuing authority.
    13. present: It names "The Department of Public Safety" as the authority issuing the evacuation order.
    14. present: "The Department of Public Safety" is named as the issuing authority.
    15. present: It names "The Department of Public Safety", the issuing authority.
    16. present: "The Department of Public Safety" is named as the issuing authority.
    17. present: It names "The Department of Public Safety", the issuing authority.
    18. present: It names "The Department of Public Safety" as the entity issuing the evacuation order.
    19. present: It names "The Department of Public Safety" as the issuing authority.
    20. present: The text identifies "The Department of Public Safety" as the issuing authority.
    21. present: It names "The Department of Public Safety", the issuing authority.
    22. present: It names "The Department of Public Safety", identifying the issuing agency.
    23. present: It names "The Department of Public Safety" as the authority issuing the evacuation order.
    24. present: "The Department of Public Safety" identifies the issuing authority.
    25. present: It names "The Department of Public Safety", the issuing authority.
  • Hazardpresent25/25

    Final assessment

    All reads agree the hazard is present; a bomb threat is named as the specific danger.

    What the threat actually is. A complete warning names the specific danger, such as a shooter, a fire, a tornado, or a gas leak, rather than a vague emergency, because people decide what to do based on what they are facing.

    See all 25 individual reads
    1. present: It names "A bomb threat", a specific hazard.
    2. present: It names "A bomb threat", a specific hazard.
    3. present: It names "A bomb threat", a specific hazard.
    4. present: It names "A bomb threat", a specific threat.
    5. present: It names "A bomb threat", a specific hazard.
    6. present: It names "A bomb threat", a specific hazard.
    7. present: It names "A bomb threat", a specific hazard.
    8. present: It names "A bomb threat", a specific hazard.
    9. present: It names "A bomb threat", a specific hazard.
    10. present: It names "A bomb threat", a specific hazard.
    11. present: It names "A bomb threat", a specific hazard.
    12. present: It names "A bomb threat", a specific hazard.
    13. present: It names "A bomb threat", a specific threat.
    14. present: It names "A bomb threat", a specific threat.
    15. present: It names a "bomb threat", a specific hazard.
    16. present: It names "A bomb threat", a specific hazard.
    17. present: It names "A bomb threat", a specific hazard.
    18. present: It names "A bomb threat," a specific hazard.
    19. present: It names "A bomb threat", a specific hazard.
    20. present: It names the hazard: "A bomb threat".
    21. present: It names "A bomb threat", a specific hazard.
    22. present: It names "A bomb threat", a specific hazard.
    23. present: It names "A bomb threat", a specific hazard.
    24. present: It names "A bomb threat", a specific hazard.
    25. present: It names "A bomb threat", a specific hazard.
  • Locationpresent25/25

    Final assessment

    Unanimous that location is present; the message cites the Art Museum, Firestone Library, Nassau Hall, and the Chapel.

    Where the threat is. Saying whether danger is in a specific building, a part of campus, or area-wide lets people judge their own proximity and choose a safe direction. Without a where, a warning is hard to act on precisely.

    See all 25 individual reads
    1. present: It says "the Art Museum, Firestone Library, Nassau Hall and the Chapel", specific buildings.
    2. present: It cites "the Art Museum, Firestone Library, Nassau Hall and the Chapel", specific buildings.
    3. present: It cites "the Art Museum, Firestone Library, Nassau Hall and the Chapel", specific buildings.
    4. present: It specifies "the Art Museum, Firestone Library, Nassau Hall and the Chapel".
    5. present: It names "the Art Museum, Firestone Library, Nassau Hall and the Chapel", specific places.
    6. present: It says "the Art Museum, Firestone Library, Nassau Hall and the Chapel", specific buildings.
    7. present: It names "the Art Museum, Firestone Library, Nassau Hall and the Chapel", specific buildings.
    8. present: It names "the Art Museum, Firestone Library, Nassau Hall and the Chapel", specific buildings.
    9. present: It cites "the Art Museum, Firestone Library, Nassau Hall and the Chapel", specific buildings.
    10. present: It names "the Art Museum, Firestone Library, Nassau Hall and the Chapel", specific buildings.
    11. present: It specifies "the Art Museum, Firestone Library, Nassau Hall and the Chapel", specific buildings.
    12. present: It cites "the Art Museum, Firestone Library, Nassau Hall and the Chapel", specific buildings.
    13. present: It cites "the Art Museum, Firestone Library, Nassau Hall and the Chapel", specific buildings.
    14. present: It names "the Art Museum, Firestone Library, Nassau Hall and the Chapel" as locations.
    15. present: It cites "the Art Museum, Firestone Library, Nassau Hall and the Chapel", specific buildings.
    16. present: It names "the Art Museum, Firestone Library, Nassau Hall and the Chapel".
    17. present: It specifies "the Art Museum, Firestone Library, Nassau Hall and the Chapel", precise locations.
    18. present: It cites "the Art Museum, Firestone Library, Nassau Hall and the Chapel," specific buildings.
    19. present: It names "the Art Museum, Firestone Library, Nassau Hall and the Chapel", specific buildings.
    20. present: It specifies "the Art Museum, Firestone Library, Nassau Hall and the Chapel".
    21. present: It says "the Art Museum, Firestone Library, Nassau Hall and the Chapel", specific buildings.
    22. present: It names "the Art Museum, Firestone Library, Nassau Hall and the Chapel", specific places.
    23. present: It names "the Art Museum, Firestone Library, Nassau Hall and the Chapel", specific buildings.
    24. present: It specifies "the Art Museum, Firestone Library, Nassau Hall and the Chapel", named buildings.
    25. present: It specifies "the Art Museum, Firestone Library, Nassau Hall and the Chapel", named buildings.
  • Guidancepresent25/25

    Final assessment

    All reads agree guidance is present; recipients are told to calmly leave the building and go to their assembly area.

    The protective action to take. A clear, specific instruction, such as shelter in place, evacuate, avoid the area, or run-hide-fight, drives faster and more correct protective behavior than describing the threat alone.

    See all 25 individual reads
    1. present: It instructs recipients to evacuate and "Calmly leave the building", protective actions.
    2. present: It instructs "Calmly leave the building and go to your ... assembly area", protective actions.
    3. present: It instructs recipients to "Calmly leave the building" and go to assembly areas, protective actions.
    4. present: It issues "an evacuation order" and instructs people to "Calmly leave the building".
    5. present: It instructs to "Calmly leave the building" and go to the assembly area, a protective action.
    6. present: It instructs to "Calmly leave the building and go to your building's designated evacuation assembly area", a protective action.
    7. present: It instructs people to "Calmly leave the building and go to your... evacuation assembly area", protective actions.
    8. present: It instructs people to evacuate, collect items, and "Calmly leave the building".
    9. present: It issues "an evacuation order" and tells people to "Calmly leave the building", protective actions.
    10. present: It instructs recipients to "Calmly leave the building" and follow evacuation steps, protective actions.
    11. present: It instructs people to "Calmly leave the building" and follow evacuation steps, protective actions.
    12. present: It instructs recipients to "Calmly leave the building" to assembly areas, a protective action.
    13. present: It instructs recipients to "Calmly leave the building and go to your building's designated evacuation assembly area", a protective action.
    14. present: It issues an "evacuation order" and instructs recipients to "Calmly leave the building", protective actions.
    15. present: It instructs people to "Calmly leave the building" and go to assembly areas, protective actions.
    16. present: It issues an "evacuation order" and tells recipients to "Calmly leave the building", protective actions.
    17. present: It instructs people to "Calmly leave the building" and "go to your building's designated evacuation assembly area", protective actions.
    18. present: It instructs recipients to "Calmly leave the building and go to your designated evacuation assembly area."
    19. present: It instructs to "Calmly leave the building and go to your building's designated evacuation assembly area", a protective action.
    20. present: It instructs recipients to "Calmly leave the building" and go to the "evacuation assembly area".
    21. present: It instructs recipients to "Calmly leave the building and go to your ... evacuation assembly area", a protective action.
    22. present: It instructs recipients to "Calmly leave the building" per the evacuation order.
    23. present: It instructs recipients to "Calmly leave the building" and go to the assembly area, a protective action.
    24. present: It instructs people to "Calmly leave the building and go to your building's designated evacuation assembly area", a protective action.
    25. present: It instructs recipients to "Calmly leave the building" and go to assembly areas, protective actions.
  • Timeabsent2/25

    Final assessment

    A strong majority finds timing absent; no clock time or date appears, with a couple reads treating This is NOT a test and the present-tense order as a recency cue.

    When the message applies. A timestamp, the word now or immediately, or a phrase like until further notice tells the reader whether the danger is current and how quickly to act.

    See all 25 individual reads
    1. absent: No clock time, date, or recency word such as "now" appears.
    2. absent: No clock time, date, or recency word appears in the text.
    3. absent: No clock time, date, or recency cue appears (NOT a test is not a time reference).
    4. present: "This is NOT a test" and present-tense order imply current recency.
    5. absent: No clock time, date, or recency cue appears in the text.
    6. absent: No clock time, date, or recency cue appears; "NOT a test" is not a time reference.
    7. absent: No clock time, date, or recency cue appears; "NOT a test" is not a time reference.
    8. absent: No clock time, date, or recency cue such as "now" or "immediately" appears.
    9. absent: No clock time, date, or recency cue beyond "This is NOT a test" is present.
    10. absent: No clock time, date, or recency cue such as "now" appears.
    11. absent: No clock time, date, or recency word appears; "This is NOT a test" is not a time cue.
    12. absent: No clock time, date, or recency cue appears in the text.
    13. absent: No clock time, date, or recency cue such as "now" appears in the text.
    14. absent: No clock time, date, or recency word like "now" appears in the text.
    15. absent: No clock time, date, or recency cue such as "now" appears in the text.
    16. absent: No clock time, date, or recency word such as "now" appears.
    17. absent: No clock time, date, or recency word appears in the text.
    18. present: "This is NOT a test" with the immediate evacuation order conveys present-time urgency.
    19. absent: No clock time, date, or recency cue such as "now" or "immediately" appears.
    20. absent: No clock time, date, or recency word is present.
    21. absent: No clock time, date, or recency cue appears; "NOT a test" is not a time reference.
    22. absent: No clock time, date, or recency cue appears; "NOT a test" is not a time cue.
    23. absent: No clock time, date, or recency cue such as "now" or "immediately" appears.
    24. absent: No clock time, date, or recency word appears; "This is NOT a test" is not a time cue.
    25. absent: No clock time, date, or recency cue appears in the text.
  • Impactpresent19/25

    Final assessment

    Present (19 of 6). The alert reports a bomb threat to named buildings and orders evacuation plus inspection, which the majority read as conveying serious danger; dissenters held it only names the threat.

    What the hazard could do to the people in its path. Beyond naming the threat, a complete warning conveys its potential consequences or severity, such as that a tornado can level buildings or that a leak could be explosive, so recipients grasp how much danger they are in. Research on warning message content finds that a concrete impact statement helps people personalize their risk and act sooner.

    See all 25 individual reads
    1. present: Orders evacuation and closure due to hurricane intensity with detailed flood-damage precautions, conveying clear danger to people and property.
    2. absent: It announces a bomb threat and evacuation order with instructions but states no harm or severity of the bombs.
    3. absent: It directs building evacuation and collection of items for a bomb threat but states no harm the bomb could cause.
    4. present: It describes a bomb threat and an evacuation order, and the instruction to leave doors open for inspection of a bomb threat conveys a danger, though impact is weakly stated; the explicit bomb-threat evacuation implies serious harm potential.
    5. present: Calls the building takeover a dangerous situation for protestors, staff, and law enforcement.
    6. present: States a bomb threat and orders evacuation of buildings, with evacuation implying danger to life from the threatened explosive.
    7. present: States the decision to close and evacuate due to Hurricane Milton and gives water-damage protective steps, conveying potential harm.
    8. absent: It reports an evacuation order for a bomb threat but states no consequence or danger of what the bomb could do.
    9. present: Issues an evacuation order for a bomb threat citing building inspection, but only naming the threat without explicit stated harm, however the directed evacuation for safety implies danger.
    10. present: It describes a bomb threat and an evacuation order and warns this is not a test, but it states no explicit harm beyond naming the threat, though the building inspection framing implies danger.
    11. present: Reports a fire in a chemistry lab requiring a first-alarm fire response, indicating a destructive hazard.
    12. present: A bomb threat with an evacuation order plus instructions to leave doors open for inspection implies the danger of an explosive device threatening the buildings.
    13. present: States the bomb threat is NOT a test and orders evacuation, and the explicit not-a-test emphasis plus bomb threat conveys serious danger, though it is borderline; the evacuation framing implies harm.
    14. present: It reports a bomb threat and orders evacuation, and a bomb threat with an active evacuation order strongly implies risk of explosion and harm.
    15. present: The text states an evacuation order with the instruction to collect car keys and leave for inspection in response to a bomb threat, and evacuation for safety implies the hazard's danger.
    16. present: Identifies a real bomb threat and orders evacuation, with the bomb threat plus evacuation implying potential lethal harm.
    17. present: It reports a bomb threat to multiple buildings and issues an evacuation order to allow inspection, an explicit threat with evacuation for safety.
    18. present: Describes an evacuation order for buildings to allow inspection of a bomb threat, implying serious danger requiring people to leave for safety.
    19. present: States a bomb threat was received and orders evacuation with detailed inspection steps, and the bomb threat with evacuation conveys implied danger to people.
    20. present: Describes the takeover as creating a dangerous situation for protestors, staff, and law enforcement, explicitly stating potential harm.
    21. absent: Reports a bomb threat and evacuation order but does not state what the bomb could do or any explicit danger or severity.
    22. present: Names a bomb threat and orders evacuation while instructing to leave doors open for inspection, with the bomb threat plus evacuation implying potential for harm.
    23. present: It states the Department of Public Safety issued an evacuation order for a bomb threat, implying serious danger requiring building evacuation.
    24. absent: Reports an evacuation order for a bomb threat with instructions but states no explicit harm or severity of the bomb.
    25. absent: It announces a bomb threat and evacuation order but states no harm or severity of the threat.

Systematic AI judgments with visible reasoning, not human-validated codings.

About this analysis
Context

Background

On the morning of September 19, 2020, Princeton University's Department of Public Safety received a bomb threat claiming that improvised explosive devices had been placed in four buildings on the main campus. The threat targeted some of the university's most historically significant structures, including Nassau Hall, which dates to 1756 and briefly served as the capitol of the United States. The campus was operating under COVID-19 restrictions at the time, with reduced in-person activity. A multi-agency investigation eventually led to the arrest of a 15-year-old from Saskatoon, Canada, who was apprehended at his grandparents' home in South Vacherie, Louisiana, in March 2021. The investigation involved the Regional Enforcement Allied Computer Team in California, the U.S. Secret Service, the FBI Joint Terrorism Task Force, and Edmonton city police. The teen pleaded guilty and was found to be connected to multiple swatting incidents across the country.
Analysis

Key Findings

The TigerAlert evacuation order went out at 11:11 a.m. EDT and the all-clear followed at 1:05 p.m. EDT, after law-enforcement sweeps of all four buildings, a roughly two-hour disruption
The four targeted buildings represent Princeton's administrative, academic, spiritual, and cultural centers, maximizing disruption
The arrest of a 15-year-old Canadian teen six months later demonstrated the cross-border complexity of swatting investigations
COVID-19 restrictions meant the campus was less populated than usual, reducing the number of people directly affected by the evacuation
Outcome
No explosive devices were found. A 15-year-old from Saskatoon, Canada, was later arrested in Louisiana in March 2021 and pleaded guilty to the swatting call.
Provenance

Sources

  1. Official
    UPDATE: All clear following bomb threat - Princeton University
    princeton.edu
    archived copy
  2. Student Paper
    U. issues 'All Clear' following bomb threat - The Daily Princetonian
    dailyprincetonian.com
    archived copy
  3. News
    Saskatoon teen charged with swatting bomb threat at Princeton University - CBC News
    cbc.ca
    archived copy
  4. News
    Teen Charged In Bomb Threat At Princeton University - Patch
    patch.com
    archived copy
Cite this case

Campus Alert Archive. "Princeton University: Bomb threat against four landmark buildings; all cleared within about two hours." Incident of September 19, 2020. Added May 2026; last updated July 2026. https://campusalertarchive.com/case/princeton-university-bomb-threat-2020-09-19/

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Alert text quoted on this page remains the work of the issuing institution; the archive is a secondary source.

Tags
bomb-threatswattingevacuationivy-leaguecovid-erateen-suspectnew-jerseynassau-hallHoax
Added May 2026Updated July 2026Via ingestion