BERKELEY, Calif. (KRON) — Berkeley Police arrested a 15-year-old boy for possession of a BB-gun at Berkeley High School Wednesday morning, police said.

Officers responded to a report around 11:53 a.m. involving two students fighting. Police learned a student threatened another with a handgun, officials say.

The boy holding the gun was not a Berkeley High School student.

A school resource officer was able to identify the students and help the police. Officers chased down the students and detained them.

Officers say they found the gun in one student’s backpack and mistook it for a real weapon. The BB-gun was modified to look like a firearm.

The student with the gun was arrested on suspicion of brandishing a replica firearm and having a weapon on campus, police said.