CHICAGO (CBS) — Several people were killed and multiple people were injured when a former student opened fire at Marjory Stoneman Douglas High School in Florida on Wednesday.

The Broward Sheriff’s Department said there were “at least 14” people transported to the hospital with varying degrees of injuries, CBS News reports.

Hundreds of students and teachers scrambled at the first sound of gunfire.

“Kids were freaking out. Some froze, some were on their phones — a lot were on their phones just trying to Snapchat everything because they thought it was a joke and it wasn’t,” said one former student, who happened to be at the school visiting a teacher.

Broward County Schools superintendent Robert Runcie is a veteran of Chicago Public Schools. “It’s just a heartbreaking tragedy,” he said. “I have, literally, come from celebrating our teachers and our district to where I am right now.”

Runcie said there was no warning or threats made before the incident, and that the shooter entered the school during a dismissal.

Ambulances converged on the scene as emergency workers appeared to be treating possibly wounded people on the sidewalks.

Some students exited the building in single-file rows with hands raised overhead to show they carried no weapons. Others held onto other students as they made their way out past helmeted police in camouflage with weapons drawn.

CBS News has confirmed that the suspect has been identified as 19-year-old Nicholas Cruz.

The suspect, who had “at one time” attended the school but was no longer enrolled, was taken into custody without incident off campus.

Officials have not released an exact number of fatalities.