The chief of police for the Dallas Independent School District says the student who shot four students when he opened fire at a Dallas high school this week was in and out of the building in less than two minutes and is believed to have been targeting a specific student.

Hours after the shooting, a 17-year-old suspect turned himself in at the Lew Sterrett Justice Center in Dallas and was booked into Dallas County jail at 9:32 p.m., records show. Charges included aggravated assault/mass shooting.