The suspect in a deadly high school
shooting in
Parkland,
Florida, is in custody, the Broward County Sheriff's Office said.
The sheriff's office responded to reports of a shooting at Marjory Stoneman Douglas High School in Parkland shortly before 3 p.m.
US Sen. Bill Nelson told CNN's Jake Tapper that the superintendent of schools in Parkland "believes there are a number of fatalities."
Aerial footage from WSVN showed a number of people lying on the ground outside the school, being treated for injuries and moved to ambulances. As students streamed away from the school, some ran while others walked quickly in orderly lines with their hands on or above their heads.
Nicole Baltzer, 18, said she was in trigonometry class about 10 minutes before the end of the school day when the fire alarm went off. As students evacuated, she heard six gunshots and everyone started running back inside the school, Baltzer told CNN's Sara Ganim.
"I heard so many gunshots, at least like six. They were very close," Baltzer said.
Baltzer said she is still on lockdown in a classroom on the second floor. Her stepsister is also on lockdown in a different classroom, she said.
"Everyone just started freaking out," a student told CNN affiliate WSVN.
"We all thought it was a fire drill because we had one previously today," he said. "And we thought it was, so no one was that nervous, but then word started going around that it was shots and not just, like, something else, everyone just started running towards the canal."
Lissette Rozenblat told CNN that her daughter safely evacuated the school and was taking shelter at a nearby Walmart.
"She was very nervous, she said that she could hear the person who was shot crying out for help, and was just a nervous wreck," Rozenblat said.
Dozens of law enforcement vehicles are on site, including one tank, along with a team of heavily armed law enforcement officers. Agents from the Miami office of the Bureau of Alcohol, Tobacco, Firearms and Explosives are responding to the scene, a spokesman said.
Parkland is a city of more than 20,000 people outside Boca Raton in Broward County, Florida. Stoneman Douglas High School had an enrollment of about 3,100 students in the 2015-16 year, according to the National Center for Education Statistics.
Clarification: Earlier reports from WSVN said that 20 people may have been injured. CNN has not confirmed the number of injured. This is a developing story and will be updated.