Campus Alert Archive
Mt. SAC

A 10:24 A.M. Bomb Threat Naming a 2:45 P.M. Detonation Time Evacuated Mt. SAC and Locked Down Walnut High School Across the Street

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

On the morning of Thursday, March 24, 2016, Mt. San Antonio College — one of the largest community colleges in California — was evacuated and adjacent Walnut High School was placed on lockdown after a bomb threat was received naming a 2:45 p.m. PDT detonation time. Los Angeles County Sheriff's deputies with bomb-sniffing dogs swept both campuses. The threat was determined to be a hoax: LASD tweeted at 1:22 p.m. PDT that the threat had concluded and the Walnut High lockdown was lifted, and Mt. SAC tweeted at approximately 3:11 p.m. PDT that the campus was clear with classes resuming at 4:30 p.m. PDT. 18-year-old Adrian Mendoza of West Covina, enrolled at both Walnut High School and Mt. SAC, was arrested on April 8, 2016 on suspicion of making a false report of a bomb or explosive device.

Alerts
3
Response
6 min
Killed
0
Injured
0
Institution
Mt. San Antonio College
Community College · CA
~29,000 studentsMt. SAC Alerts
Confirmed Timeline

Alert Sequence

3 messages in sequence · 1 verified verbatim

Some alert texts below are approximate reconstructions from news coverage, not confirmed verbatim transcripts. Reconstructed texts are shown in italic with a dashed border. Verified verbatim texts have a solid border and are marked accordingly.

INITIAL ALERTSMS
Verified verbatimABC7 Los Angeles, quoting the Mt. SAC emergency alert text message sent to students126 chars
EMERGENCY ALERT: Report of threat to campus at 2:45pm. Calmly leave campus. Classes/services are closed until at least 4:30pm.
The emergency alert text quoted the named threat time (2:45 p.m. PDT) directly to students, an unusual choice that gave the campus community a clear deadline to be away from buildings
The alert directed students to 'calmly leave campus' rather than evacuate to a specific location — a less prescriptive approach reflecting Mt. SAC's commuter character
Mt. SAC enrolls approximately 29,000 students and is one of California's largest community colleges; the named 4:30 p.m. service-closure time created a structured operational window
UPDATEEmail
Approximate reconstruction333 chars
Mt. SAC Update: The campus remains evacuated while the Los Angeles County Sheriff's Department conducts a search with bomb-detection K-9 units. Faculty, staff, and students should not return to campus until further notice. Morning classes are canceled. A decision on afternoon and evening operations will be communicated by 1:30 p.m.

This text has been reconstructed from news coverage and may not reflect the exact original wording.

The 1:30 p.m. PDT decision deadline was set deliberately ahead of the 2:45 p.m. PDT named detonation time, giving administrators a clear governance window
LASD's deployment of bomb-sniffing dogs is the standard protocol for community-college bomb threats in Los Angeles County
The CBS Los Angeles report noted that Mt. SAC's evening classes were specifically the operational decision in question, given the late-afternoon timing of the named threat
ALL CLEARSMS
Approximate reconstructionReconstructed from CBS Los Angeles reporting on Mt. SAC's 3:11 p.m. PDT tweet declaring campus safe and resumption of classes at 4:30 p.m. PDT248 chars
Mt. SAC Alert: The campus has been cleared by LASD. The bomb threat has been determined to be a hoax. Classes will resume at 4:30 p.m. Daytime classes that were canceled will not meet today. Counseling support is available through Student Services.

This text has been reconstructed from news coverage and may not reflect the exact original wording.

Mt. SAC tweeted at 3:11 p.m. PDT that the campus had been deemed safe by authorities and that classes would resume at 4:30 p.m. PDT — about 26 minutes after the named 2:45 p.m. PDT detonation time
Earlier, at 1:22 p.m. PDT, LASD had tweeted that the bomb threat had concluded and the lockdown at Walnut High School had been lifted; Mt. SAC's all-clear was issued separately because campus officials chose to keep its evacuation in place pending their own bomb-detection sweep
CBS Los Angeles reported that Mt. SAC's evening classes did resume — an operational signal that administrators had high confidence in the hoax determination
Context

Background

Mt. San Antonio College — known as Mt. SAC — is one of the largest community colleges in California, located in Walnut, eastern Los Angeles County. On the morning of Thursday, March 24, 2016, at 10:24 a.m. PDT, Mt. SAC and adjacent Walnut High School received a bomb threat that named a 2:45 p.m. PDT detonation time — an unusually specific time, which gave the Los Angeles County Sheriff's Department and Mt. SAC administrators a four-hour window to act. Mt. SAC was evacuated; Walnut High School, where students were minors who could not be released without parent pickup, was placed on lockdown. LASD deputies with bomb-detection K-9 units swept both campuses. At approximately 1:22 p.m. PDT, LASD tweeted that the threat had concluded and the lockdown at Walnut High School had been lifted. Mt. SAC's separate all-clear came at approximately 3:11 p.m. PDT — about 26 minutes after the named detonation time — and the college announced that classes would resume at 4:30 p.m. PDT. On April 8, 2016, 18-year-old Adrian Mendoza of West Covina — enrolled at both Walnut High School and Mt. SAC — was arrested on suspicion of making a false report of a bomb or explosive device. The case is significant for the campus alert archive because it documents joint community-college and K-12 emergency-management coordination — a pattern recurring in California, where many community colleges sit immediately adjacent to high schools, and because the named-time bomb threat created an unusually structured decision window for administrators and law enforcement.
Analysis

Key Findings

The bomb threat named a specific detonation time (2:45 p.m. PDT) that gave administrators an unusually structured four-hour decision window
Mt. SAC was evacuated while adjacent Walnut High School was placed on lockdown — different protocols reflecting K-12 vs community-college student-release rules
LASD bomb-detection K-9 units swept both campuses, the standard Los Angeles County protocol for community-college bomb threats
Walnut High School's lockdown was lifted at 1:22 p.m. PDT after LASD tweeted that the threat had concluded; Mt. SAC's separate all-clear was issued at approximately 3:11 p.m. PDT, with classes resuming at 4:30 p.m. PDT
On April 8, 2016, 18-year-old Adrian Mendoza of West Covina — enrolled at both Walnut High School and Mt. SAC — was arrested on suspicion of making a false report of a bomb or explosive device
Outcome
No device was found. The Walnut High School lockdown was lifted at 1:22 p.m. PDT after LASD tweeted the conclusion of the threat. Mt. SAC tweeted at approximately 3:11 p.m. PDT that the campus was clear, with classes scheduled to resume at 4:30 p.m. PDT. The threat was treated as a hoax; LASD bomb squad with K-9 units cleared both campuses well before the named 2:45 p.m. PDT detonation time. On April 8, 2016, 18-year-old Adrian Mendoza of West Covina — enrolled at both Walnut High School and Mt. SAC — was arrested on suspicion of making a false report of a bomb or explosive device.
Provenance

Sources

  1. News
    Bomb threat closes Mt. SAC College, prompts lockdown of Walnut High School (ABC7 Los Angeles)
    abc7.com
  2. News
    Mount San Antonio College Evacuated Amid Possible Bomb Threat; Walnut High School on Lockdown (KTLA)
    ktla.com
  3. News
    All-Clear Given After Bomb Threat at Mt. San Antonio College (NBC Los Angeles)
    nbclosangeles.com
  4. News
    Evening Classes To Resume At Mount San Antonio College In Walnut Following Threat (CBS Los Angeles)
    cbsnews.com
  5. News
    Mt. San Antonio College, Walnut High declared safe after bomb threat (89.3 KPCC)
    archive.kpcc.org
  6. Student Paper
    Bomb threat closes Mt. SAC and Walnut High School (Campus Times)
    lvcampustimes.org
  7. News
    18-Year-Old Student Arrested in False Bomb Threat at Mt. San Antonio College (NBC Los Angeles)
    nbclosangeles.com
Tags
bomb-threatcommunity-collegecaliforniawalnutlos-angeles-countyk-12-coordinationnamed-detonation-timeevacuationlasd-bomb-squadk9-sweepHoax
Added May 2026Updated May 2026Via ingestion