A heavily armed young man barged into his former high school about an hour northwest of Miami on Wednesday, opening fire on terrified students and teachers and leaving a death toll of 17 that could rise even higher, the authorities said.
Students huddled in horror in their classrooms, with some of them using their cellphones to record the carnage, capturing victims, screams, and gunfire. The dead included students and adults, some of whom were shot outside the school and others inside the three-story building.
The gunman, armed with a semiautomatic AR-15 rifle, was identified as Nikolas Cruz, a 19-year-old who had been expelled from the school, the authorities said. He began his shooting rampage outside Marjory Stoneman Douglas High School in Parkland, Florida, shortly before dismissal time around 2:40 p.m. He then made his way inside and went down hallways he knew well, firing at students and teachers who were scurrying for cover, the authorities said.
“Oh my God! Oh my God!” one student yelled over and over in one video circulating on social media, as more than 40 gunshots boomed in the background.
By the end of the rampage, Cruz had killed 12 people inside the school and three outside it, including someone standing on a street corner, Broward County Sheriff Scott Israel said. Two more victims died of their injuries in local hospitals.
On Thursday, the authorities charged Cruz with 17 counts of premeditated murder.
“This is catastrophic,” said Sheriff Israel, who has three children who graduated from the high school. “There really are no words.”
Cruz was arrested in Coral Springs, a neighboring city a couple of miles from the school, about an hour after fleeing the scene, the authorities said. He had slipped out of the building by mixing in with crowds of students. In addition to the rifle, Sheriff Israel said Cruz had many additional rounds of ammunition.
The gunman had clearly prepared for the attack, Senator Bill Nelson of Florida said in an interview after speaking to the F.B.I.
“The shooter wore a gas mask, had smoke grenades, and he set off the fire alarm so the kids would come out of the classrooms,” said Nelson, citing details he learned from the F.B.I. Several students said they found it strange to hear the alarm, because they had already had a fire drill earlier in the day.
Sheriff Israel said he didn’t know the gunman’s motive. He said a football coach was among the dead, and the son of a deputy sheriff among the injured. Twelve of the 17 dead had been identified by Wednesday night, he added, noting that not all of the students had backpacks or wallets on them.