Karl Pierson ID'd As Arapahoe High School Shooting Suspect

Authorities have identified 18-year-old Karl Pierson as the student who allegedly opened fire at Arapahoe High School in Centennial, Colo. on Friday afternoon.

At a press conference, Sheriff Grayson Robinson said the suspect entered the school armed with a shotgun and asked for a specific teacher. When that teacher heard that the armed student was asking for him, he left the school immediately, and was uninjured. The suspect then opened fire, leaving one 15-year-old girl in critical condition.

Pierson died of a self-inflicted gunshot wound.

This story has been updated to reflect the number of students injured.