A student was left in critical condition after a shooting at Arapahoe High School in Centennial, Colo. on Friday.

A 15-year-old girl was taken to a hospital with serious injuries, though previous reports suggested a second student was wounded by the gunman.

Authorities identified the shooting suspect Friday night as 18-year-old student Karl Pierson.

County Sheriff Grayson Robinson said at an afternoon press conference that the suspect died from a self-inflicted gunshot wound. Authorities “found his body in the internal portion of the school in a classroom.” The shooter is believed to have acted alone.

The shooter “targeted a specific teacher that he was interested in confronting,” according to Robinson.