OMAHA, Neb. — Omaha police arrested a suspect about half an hour after a shooting Tuesday that critically injured a teenage boy at a high school in Nebraska’s largest city.

Families rushed to Omaha Northwest High School after the shooting was reported by the school resource officer during lunch at 12:23 p.m. Omaha Police Deputy Chief Sherie Thomas said officers from several departments quickly responded to the school and found the victim inside.

Thomas said police believe the shooting was an isolated incident between two students. The suspect was arrested three blocks away about 30 minutes later.

Parents tearfully embraced their kids in the parking lot as the first few started to come out of the school after 1 p.m. Police set up a reunification site at the football stadium, but said it would be a long process to release all the students.

Thomas said a 15-year-old boy was critically injured in the shooting and rushed to a hospital.

One student told KETV that he was coming back to school after lunch and ran as fast as he could when he heard screams and saw people running because he didn’t want to die.

Two nearby Catholic high schools — Marian and Roncalli high schools — were also locked down after the shooting, but that was lifted after the arrest.

Devon DeMott told the Omaha World-Herald that he raced to the school from his home a few blocks away as soon as his son texted him there had been a shooting.

“As fatherly instinct, I jumped in the car and headed up there,” said DeMott, who was glad to see a significant police presence when he arrived.

The school district canceled all Tuesday evening activities at Northwest High and all classes on Wednesday. Students are scheduled to return Thursday.