Los Angeles County Sheriff's deputies seized rifles, handguns, ammunition and dozens of "high-capacity" magazines from the Norwalk home of a student at El Camino High School in south Whittier last week after a resource officer overheard the teenager threatening to shoot up the school.

The student, who remains unnamed because he is a minor, was arrested by deputies on suspicion of making criminal threats on Friday, according to Los Angeles County Sheriff Jim McDonnell.

Also arrested was one of his older brothers, 28-year-old Daniel Eriberto Barcenas, a U.S. Army veteran — deputies said the brother told them the weapons belonged to him. Barcenas was arrested on multiple weapons charges, including possession of an "assault rifle" and failure to register a firearm, the Whittier Daily News.

A resource officer for the Norwalk-La Mirada Unified School District first heard the threat, according to Robert Jacobsen, an attorney for the district. He said the officer, Marino Chavez, told district officials he heard the student talking about shooting up the school “sometime in the next three weeks.”

When deputies arrived at the home Friday they found two AR-15 rifles, two handguns and 90 high-capacity ammunition magazines, the sheriff said.