The student accused of injuring four in a shooting at a Dallas high school was let into the building through an unsecured door and then walked down a hallway toward a group of students, opening fire on them before appearing to take a point-blank shot at one.

Five students were injured in a shooting Tuesday afternoon at Wilmer-Hutchins High School in southeast Dallas when a 17-year-old allegedly snuck into the school and fired “indiscriminately,” according to a state affidavit for the suspect’s arrest warrant.