An alert security guard overheard a student threatening to open fire at his Southern California high school days after a massacre in Florida, and a swift investigation uncovered two assault rifles and nearly 100 high-capacity magazines at his home, authorities said Wednesday.
Although the 17-year-old claimed his comment was a joke and investigators didn't uncover a specific plot, the head of the nation's largest sheriff's department said it shows the need to take every potential threat seriously.
"This is an example of something that could have potentially went down that path, but didn't," Los Angeles County Sheriff Jim McDonnell said, referencing the Florida high school shooting last week that killed 17. "As we see these incidents occur one after another, we're all looking to say how do we stop this?"
A national organization that tracks school threats says it's recorded about 50 a day on average since the Florida shooting, compared with about 10 a day on average.
School security officer Marino Chavez heard the teen say Friday at El Camino High School near the city of Whittier that he was "going to shoot up the school sometime in the next three weeks" and reported the comment to authorities, McDonnell said.
Chavez said he asked the student about the threat, and the teen confirmed that he made it but was just kidding and didn't mean it. The teenager had apparently been angry that a teacher told him he couldn't wear headphones in the classroom, the guard said.
"I'm not a hero. I was just doing my job," Chavez said at a news conference.
Deputies searched the teen's home and found two AR-15 rifles, 90 high-capacity magazines and two handguns, including one that was left in a hallway laundry basket, the sheriff said.
The teenager, who had an extensive disciplinary history at the school, was arrested on suspicion of making a criminal threat and was in custody, McDonnell said.
His 28-year-old brother, Daniel Eriberto Barcenas, told deputies that he purchased the guns while serving in the Army in Texas. One of the rifles wasn't registered, which is a felony in California, McDonnell said.
The brother is facing charges of possession of an assault weapon, importing a high-capacity magazine and other violations.
The brothers lived with their parents, and there was no indication the parents committed a crime, authorities said.
"We take all the threats we receive seriously," he said. "Anytime we can get a chance to prevent something like that happening, we all come away from that very relieved."
School threats on the rise nationwide since the Florida shooting include dozens on social media, about 10 incidents where a gun was brought to school and 22 bomb threats, said Amy Klinger, director of programs for the Ohio-based Educators School Safety Network.
An Oregon high school student was arrested Wednesday on suspicion of disorderly conduct after police say he sent a social media message to a girl at another high school reading, "I am the shooter!" The 15-year-old boy said the message was a joke.
A Montana high school student was charged Tuesday with intimidation and assault with a weapon over numerous threats to "shoot up the school." Court records say the 18-year-old told investigators he was joking and regretted frightening students.
A Vermont teenager pleaded not guilty Friday to attempted aggravated murder and other offenses after writing in a diary that he had "big plans" to kill as many as he could at his former high school.
In Northern California, police said they recovered a firearm from the home of an 11-year-old boy who had barricaded himself in a Santa Cruz classroom Tuesday and planned to harm specific students.
This story has been updated.