Florida school shooter: What we know about gunman Nikolas Cruz

The teenager blamed for the Florida high school shooting has been described as a "gun-obsessed" and troubled former student by police and former classmates.

Nikolas Cruz, 19, had been expelled from Florida's Marjory Stoneman Douglas High School for disciplinary reasons, according to media reports, but he returned to the school to carry out the massacre.

Seventeen people died and dozens of others are now receiving treatment for gunshot wounds, after the mass shooting broke out on Wednesday afternoon (local time). Cruz was arrested about an hour later.

  • Armed with multiple ammunition magazines and one AR-15-style rifle
  • Expelled from the school last year for unknown 'disciplinary reasons'
  • Described as a troubled classmate who was "crazy about guns"
  • Reportedly banned from campus after threatening students
  • Had "disturbing" material on social media accounts

Broward County Sheriff Scott Israel told reporters that there were signs, before the shooting, that Cruz was disturbed.

"We already began to dissect his websites, and the things on social media that he was on and some of the things that came to mind are very, very disturbing," Mr Israel said.

Matthew Walker, a student at the school, told WFOR-TV that all his classmates "knew it was going to be him".

"A lot of people were saying it was going to be him," he said.

"A lot of kids threw jokes around, saying that he was going to be the one to shoot up the school. It turns out that everyone predicted it. That's crazy.

"He was going class to class, just shooting at random kids," Mr Walker continued.

"Everything he posts [on social media] is about weapons. It's sick."

Chad Williams, 18, remembered Cruz as a troubled classmate when they attended middle school together.

He said Cruz would set off the fire alarm, day after day, and finally got expelled in the eighth grade.

More recently, Mr Williams saw Cruz carrying several publications about guns, when they ran into each other at the high school.

"He was crazy about guns," Mr Williams said.

"He was kind of an outcast. He didn't have many friends. He would do anything crazy for a laugh, but he was trouble."

Jillian Davis, 19, said she was in a school Junior Reserve Officer Training Corps with Cruz in the ninth grade.

She remembered him as a quiet and shy young man, who would almost change personality when angry.

He talked a lot about guns and knives, but no-one took him seriously, she said.

"I would say he was not the most normal or sane kid... he definitely had a little something off about him," said Ms Davis, who graduated from the school last year. "He was a little extra quirky."

Maths teacher Jim Gard told the Miami Herald that Cruz had been banned from returning to campus, while carrying a backpack.

"There were problems with him last year, threatening students, and I guess he was asked to leave campus," Mr Gard told the newspaper in an interview.

Reuters / Newshub.