WARNING - DISTRESSING CONTENT: Seventeen people have been killed after a gunman opened fire at a US high school.
The violence erupted shortly before dismissal at Marjory Stoneman Douglas High School in Parkland, about 72 km north of Miami. Live television footage showed students streaming out of the building as dozens of police and emergency services personnel swarmed the area.
Students hid under desks in their classroom as the gunman, suspected to be an expelled student, fired shots. Some shared images from their class as the terror unfolded.
The gunman was identified as 19-year-old Nikolaus Cruz, who previously attended the school and was expelled for unspecified disciplinary reasons, Broward County Sheriff Scott Israel said at a news briefing hours later.
The gunman surrendered to police without a struggle, Israel said. Investigators believe he was armed with an AR-15-style rifle and had multiple magazines of ammunition, according to the sheriff.
"It's catastrophic," Israel said. "There really are no words."
Twelve of the dead were killed inside the school, two others just outside, one more on the street and two other victims died of their injuries at a hospital, Israel said. He said the victims comprised a mixture of students and adults.
Staff and students told local media that a fire alarm went off around the time the shooting started, sparking chaos as some 3300 students at the school first headed into hallways before teachers herded them back into classrooms, to seek shelter in closets.
Kyle Yeoward, a 16-year-old junior, told Reuters he was in the bathroom on the second floor of a building when he heard two shots.
"He let loose on the freshman building," Yeoward said.
CBS News posted a brief clip of cell phone video footage the network said was taken from inside a classroom, showing what appeared to be several students. A rapid series of loud gunshots are heard amid hysterical screaming and someone yelling, “Oh my God.”
McKenzie Hartley, 19, who identified herself as the sister of a student at the school described the scene in a text message to Reuters: "She heard him shooting through the windows of classrooms and two students were shot."
Some students exited the building in single-file rows with hands raised overhead to show they carried no weapons.
Others held onto other students as they made their way out past helmeted police in camouflage with weapons drawn.
- Terrifying video from inside classroom as shots fired
- Terrified students share photos from inside classroom
- School had sent out warnings about suspect, teacher said
Police officers in helmets, bulletproof vests and armed with automatic weapons could be seen stationed at several points around the school.
TV footage showed at least one person being wheeled to an ambulance on a gurney while emergency workers appeared to be helping others on the sidewalk.
IIt was the 18th shooting in a U.S. school so far this year, according to gun control group Everytown for Gun Safety.
That tally includes suicides and incidents when no one was injured, as well as the January shooting in which a 15-year-old gunman killed two fellow students at a Benton, Kentucky, high school.
President Donald Trump offered his condolences to those impacted by the shooting.