Seventeen people, including students, were killed and over a dozen injured at a Florida school on Wednesday after a 19-year-old former student opened fire. The gunman, identified as Nikolaus Cruz, was arrested in a neighbouring city about an hour later, The New York Times reported.

Parkland’s Marjory Stoneman Douglas High School had earlier expelled Cruz for disciplinary reasons, authorities said.

The incident took place shortly before dismissal time at 2.40 pm (1.10 am Thursday Indian time). After students and staff heard “what sounded like gunfire”, the school went into lockdown, said the school district on Twitter.

“The shooter went and set off the fire alarm so the kids would come pouring out of the classrooms into the hall,” Bill Nelson, a US senator told reporters, The Guardian said.

Students were seen running out of the building as the police and emergency services personnel moved inside, Reuters reported.

Football coach Aaron Feis jumped in front of students to protect them from the shooter, The Miami Herald reported. Broward County Sheriff Scott Israel later announced that Feis had died. “This is catastrophic,” Israel said about the shooting. “There really are no words.”

“I’m absolutely sick to my stomach to see children who go to school with backpacks and pencils lose their lives,” he said according to The Guardian. He said that investigators who looked at Cruz’s social media pages on Wednesday found “very, very disturbing” things, but he did not elaborate.

Israel added at a press conference that 12 of the 17 victims had been identified, though their names had not yet been released to their families. Doctors at Broward Health said 17 patients, including the shooter, were taken to three hospitals in the area. Emergency Medical Director Igor Nichiporenko said that the three patients who needed surgery would recover fully.

This was the 18th shooting in a school in the United States so far in 2018, said a gun control group, Everytown for Gun Safety.

Soon after the shooting incident, President Donald Trump said on Twitter that “no child, teacher or anyone else should ever feel unsafe in an American school”.