YUCAIPA, Calif. (AP) – Authorities say a 16-year-old Southern California student was arrested at home in possession of a loaded handgun after school staff received a tip that the boy was armed.

The San Bernardino County Sheriff’s Department says the arrest came after security was beefed up at Yucaipa High when a message threatening a campus shooting was found scrawled in a bathroom.

Investigators say they’ve found no evidence that the threat is credible and don’t know who wrote it.

A sheriff’s statement says there was no shooting, no gun found on campus and no one was injured.

The student had a loaded .22 caliber handgun. He could face charges including minor in possession of a firearm.

The arrest comes less than a week after a 16-year-old boy fatally shot two classmates and himself at a school near Los Angeles.