Four students were injured, including three with gunshot wounds, after a shooting at Wilmer-Hutchins High School in Dallas on Tuesday afternoon, officials said.

Officials with Dallas Fire-Rescue confirmed the injuries and said the patients’ ages were 15 to 18. They had injuries that ranged from serious to non-life-threatening, the agency said.

Students were seen evacuating the main school building after the shooting was reported to authorities around 1 p.m.

“I turned around, all I heard was seven gunshots. I grabbed a teacher and ran in the room,” student Patrick Campos said. “Running, everybody was running.”

In a brief news conference Tuesday afternoon, Dallas ISD police and district officials said the gunman had been identified but was at large. Hours later, the suspect was arrested and was being held in the Dallas County Jail.

The school is the same one where a student was injured in a shooting in a classroom last year.

“Today as we all know, the unthinkable has happened,” Dallas Independent School District Superintendent Stephanie Elizalde said. “And quite frankly, this is just becoming way too familiar, and it should not be familiar.”

The district said the gun did not enter the school building during the primary intake period when students pass through metal detectors.

District officials would not say how the gun made its way into the building or what happened in the moments before shots were fired.

“We do have the identity of the suspect, but as I mentioned earlier, this is still a very fresh and fluid investigation, so I don’t have any other information regarding what led up to the shooting,” district police Assistant Chief Christina Smith said.

District leaders said classes would be canceled at the school through the rest of the week and counselors would be made available to anyone struggling after the shooting.