Authorities say have they thwarted a "disgruntled" student's plan to carry out a mass shooting at a high school in Whittier.
An on-campus security officer at El Camino High School overheard the student threaten to shoot up the school and alerted deputies Friday, according to the Los Angeles County Sheriff's Department.
Investigators seized a "collection of weapons and ballistic evidence" from the student's home, authorities said.
A news conference was scheduled for Wednesday morning.
11:30 p.m.: This article was updated with staff reporting.