Authorities say the 19-year-old man accused of the shooting walked into the Marjory Stoneman Douglas High School in Parkland, near Miami, on Wednesday and opened fire.
The ex-student, identified as Nikolas Cruz, opened fire with an AR-15-style assault rifle in the second-deadliest shooting at a public school in US history.
Police said Cruz fled the scene by joining a the crowd of distressed students who were escaping the violence.
Cruz was later arrested outside, some distance from the school in an adjacent community.
FLORIDA SHOOTING HIGH SCHOOL VICTIMS IDENTIFIED
He has now been charged with 17 counts of premeditated murder. (LINK) /news/world/919333/florida-shooting-massacre-Nikolas-Cruz-photo-Marjory-Stoneman-Douglas-High-School
A mugshot released by police shows Cruz staring blankly at the camera, wearing a black t-shirt.
Cruz appeared in court today. His court-appointed lawyer said he had expressed remorse for his crimes.
In the brief court appearance, Cruz spoke only two words, “Yes ma’am,” when a judge asked him to confirm his name. He was ordered held without bond.
Police and former classmates said Cruz loved guns and had been expelled from high school for disciplinary reasons.
Authorities said he marched into the school wearing a gas mask and tossed smoke grenades, as well as pulling a fire alarm that sent students and staff pouring from classrooms as he began his rampage, according to Florida’s two US senators, who were briefed by federal authorities.
Among the victims of the massacre, twelve were killed inside the school, two just outside and one on the street, while two further victims died from their wounds in hospital.
The 17 victims include a high school football coach, an Iraq war veteran and a teenage girl.
Profiles of the victims have begun to emerge, including assistant football coach Aaron Feis, who was fatally wounded as he shielded students from a burst of gunfire from an assault rifle.
Chris Hixon, a staff member and a 49-year-old father, was a military veteran who had served in Iraq in 2007, the Sun Sentinel reported.
Dan Jacob, the athletics director at Coral Springs High School, said: “Chris is probably the nicest guy I have ever met. He would give you the shirt off his back.
“He does so much. That is terrible that it would happen to anybody. It is so senseless. I am totally crushed.”
Broward Country Sheriff Scott Israel said investigators are dissecting Cruz’s social media posts, adding: “Some of the things that have come to mind are very, very disturbing.”
Wednesday’s shooting was the 18th in a US school this year, according to gun control group Everytown for Gun Safety.