(Auburn, CA) — A 15-year-old boy is behind bars after a concerning social media post prompted the lockdown of Placer High School in Auburn. The boy is accused of posting threatening messages and a photo of a gun on social media on Tuesday.

Administrators say the boy is not a student at the school, but was on campus for a short time.

The boy left Placer High School by the time police arrived and was later arrested at his home. Students first alerted administrators of the potential threat.