A high school student is in police custody on several charges after police say he brought a loaded 9mm handgun to Tilden High School, prompting heightened security measures as students prepare to return to class.

School safety agents discovered the firearm in the 16-year-old student’s backpack while conducting routine security scans Tuesday afternoon.

The incident occurred as the student returned to the school around 4:15 p.m. for after-school activities, following earlier dismissal.

As the student walked through a security scanner, alarms sounded.

Authorities quickly took the teenager into custody. He now faces four charges of criminal possession.

Due to the teen being a minor, police have not released his identity.

It's still not clear why the teen brought the gun to school.

The Department of Education says they will be implementing additional safety measures at the school today.