PARKLAND - A former student armed with an AR-15 rifle opened fire at a Florida high school on Wednesday, killing at least 17 people, officials said.
The harrowing shooting spree saw terrified students hiding in closets and under desks as they texted for help.
Broward County Sheriff Scott Israel identified the gunman as Nikolas Cruz (19), a former student at Marjory Stoneman Douglas High School in Parkland who had been expelled for "disciplinary reasons."
Cruz was arrested without incident in the nearby town of Coral Springs after the Valentine's Day rampage and taken to hospital with minor injuries, the sheriff said.
"We have already begun to dissect his websites and things on social media that he was on and some of the things... are very, very disturbing," Israel said.
"He had countless magazines, multiple magazines, and at this point, we believe he had one AR-15 rifle," the sheriff added.
Israel said both students and adults had been killed. He was uncertain about the exact number of people injured, but at least 14 were taken to hospital and two had died there of their wounds.
The shooting, one of nearly 20 since the start of the year, will once again throw the spotlight on the epidemic of gun violence in the United States and the ready accessibility of weapons in a country with 33,000 gun-related deaths annually.
"This is a terrible day for Parkland," Israel said, speaking of the city of about 30,000 people.
A teacher at the school told The Miami Herald that Cruz had been identified previously as a potential threat to his classmates.
"We were told last year that he wasn't allowed on campus with a backpack on him," math teacher Jim Gard said. "There were problems with him last year threatening students, and I guess he was asked to leave campus."
Cruz was also said to have been in the Junior ROTC (Reserve Officers' Training Corps) program while at school.
A law enforcement source told CBS News that the gunman pulled a fire alarm before opening fire, but Israel said he could not confirm that report.
The FBI said it was assisting local law enforcement with the investigation.
When asked about security, Hunschofsky said a police officer is always stationed at the school and there was a "single point of entry."
President Donald Trump offered his "prayers and condolences to the families of the victims.
"No child, teacher or anyone else should ever feel unsafe in an American school," he said on Twitter.
My prayers and condolences to the families of the victims of the terrible Florida shooting. No child, teacher or anyone else should ever feel unsafe in an American school.— Donald J. Trump (@realDonaldTrump) February 14, 2018