Florida shooting: Suspected gunman named as expelled former student Nikolas Cruz, 19

At least 17 casualties have been identified so far

Authorities have identified the suspect in a Florida school shooting as Nikolas Cruz, a 19-year-old former student.

Broward County Sheriff Scott Israel told reporters Mr Cruz had been expelled from Marjory Stoneman Douglas High School for disciplinary reasons.

“We have already begin to dissect his websites and some of the social media he was on”, Mr Israel said, calling some of the content “very disturbing”.

At least 17 people died after a gunman opened fire from both within and outside the school. He was carrying an AR-15, a type of semiautomatic rifle, and multiple magazines.

Mr Cruz was arrested “without incident” somewhere off campus about an hour after the shooting, Mr Israel said.

A former teacher told the Miami Herald that he believed the Mr Cruz was already on the school's radar.

“We were told last year that he wasn’t allowed on campus with a backpack on him,” math teacher Jim Gard told the Herald. “There were problems with him last year threatening students, and I guess he was asked to leave campus.”

But Broward County Public Schools superintendent Robert Runcie told reporters there were no red flags giving authorities a reason to be on guard.

“We didn’t have any warnings,“ Mr Runcie said. ”There weren’t any phone calls or threats that were made“.