A teen suspect was in custody and police were seeking a motive after four students were shot in a Dallas high school where a teacher’s quick thinking was being credited for saving lives.

The rampage took place April 15 at Wilmer-Hutchins High School, said Assistant Chief Christina Smith of the Dallas Independent School District Police Department. All four students were taken to nearby hospitals to be treated for non-life-threatening injuries, Smith said.

Jason Evans, a Dallas Fire-Rescue spokesman, told the Dallas Morning News that three of the students were between the ages of 15 and 18 and that all were injured by gunfire. A 17-year-old suspect was booked into Dallas County jail at 9:32 p.m. after turning himself in, the paper reported. His bail was set at $600,000.

4 injured after Dallas school shooting; teacher credited for thwarting further violence

Police responded to the shooting shortly after 1 p.m. local time. Officials did not explain how the shooter got the gun onto campus, which requires students to walk through metal detectors and carry only clear backpacks. However, Smith said the gun was brought in outside of regular intake hours.

“So it was not a failure of our staff, of our protocols, or of the machinery that we have,” Smith said.

Teacher directed suspect away from campus

District Superintendent Stephanie Elizalde said a teacher in the classroom directed the suspect away from the school, preventing the situation from escalating.

“The teacher is a very humble individual, and he was able to direct the student away from the campus so that he could take care of, first, the injured students, and secondly, to ensure that the alleged suspect did not enter into the rest of the school building,” Elizalde told reporters. “Much more (violence) was avoided because he was directed away from the school.”