Schools in Monterey Park were locked down and the East Los Angeles College campus was evacuated after the caller threatened to "shoot up" a campus, the Los Angeles Times reported. A California Highway Patrol dispatcher said the agency received the telephone threat at 7:14 a.m. that a shooting would occur at 8 a.m. at an unspecified campus.
Authorities in Santa Monica said someone called police suggesting a 19-year-old man might shoot himself on the campus of Santa Monica College.
Santa Monica police Sgt. Candice Cobarrubias said a 19-year-old student was detained on the college campus for questioning about 9:35 a.m. The student was not armed, the Times said.
Citing an anonymous source, the Times said investigators tracked the student using his cellphone.
The student, whose name was not released, had gone to the campus psychological services facility, where police arrested him.
Los Angeles County Sheriff's Department spokeswoman Nicole Nishida said investigators had been "very diligently and methodically going through every room."
"We take every threat very seriously and this is what we're doing as a precautionary measure to ensure the safety of the students and residents," Nishida told reporters.
Richard Medina, a student at East LA College, said he saw about a half-dozen helicopters flying over the campus, and the police contingent included sheriff's deputies and California Highway Patrol officers, as well as Monterey Park police.
Authorities initially said they were not sure whether the threat was related to a similar threat at Santa Monica College, which was also put on lockdown, along with John Adams Middle School in Santa Monica.
Most of the lockdowns had been lifted by midday, the newspaper said.