Law enforcement officials seeking a motive for a shooting at Nashville’s Antioch High School on Wednesday morning are examining alarming social media posts and writings tied to a teenager police say shot and killed a 16-year-old girl.

A teenager who opened fire with a 9 mm pistol in his Nashville high school cafeteria fired a total of 10 shots within 17 seconds of entering the room, according to police.

A student opened fire inside Antioch High School, shooting two other students and then himself, the authorities said. A female student and the shooter were killed, officials said.