An AI gun detection system installed in a Nashville, Tennessee high school couldn’t spot the gun a 17-year-old used to fatally shoot another student and himself earlier this week, according to district officials.

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.

A 16-year-old female student was killed, another student was wounded, and the shooter—a 17-year-old male student—killed himself, per police.