Police say the gun used in the Nashville school shooting was purchased in Arizona as detectives piece together why the high school student fatally shot a classmate before killing himself

A 17-year-old boy who opened fire in his Nashville high school's cafeteria fired a total of 10 shots from a 9 mm pistol within 17 seconds of entering the room.

The position of the camera and the shooter led to an AI-powered weapon detection system failing to pick up on a student's gun.