A student at Bostrom High School in Phoenix was arrested Friday after carrying an AR-15-style assault rifle and a cache of ammunition in their backpack and lunch box, NBC News reports. The unidentified child was being detained at the school office when police arrested them at 1:00 p.m. local time. Police have charged them with multiple offenses, but have not detailed a reason the student brought the weapon to school or how they came to possess it.