A gunman has opened fire at a Florida high school, killing 17 people.
Sheriff Scott Israel of Broward County said the 19-year-old suspect is in custody.
The suspect, a former student at Marjory Stoneman Douglas High School in Parkland, was previously expelled for disciplinary reasons.
Swat teams swarmed the school, and the gunman was arrested without incident off campus.
Television footage showed police putting a person in the back of a police car outside the high school.
The sheriff said the gunman had at least one rifle and multiple magazines, and most of the fatalities were inside the building though some were found outside.
The suspect was later identified as Nicholas Cruz.
There were scenes of students frantically running from the building and ambulance crews treating people outside the school on Wednesday afternoon.
Broward County Superintendent Robert Runcie said: "There are numerous fatalities. It is a horrific situation."
He added: "It is a horrible day for us."
Seventeen people are dead in the shooting at a South Florida high school, the Broward County Sheriff's Office has said.
At least 14 people have been injured in a shooting at a Florida high school and "multiple fatalities" are feared, US authorities said.
The shooter is in custody, Broward County Sheriff's Office said, after Swat teams swarmed Marjory Stoneman Douglas High School in Parkland.
Broward County Sheriff confirms “multiple” people were killed in school shooting.
— Veronica Rocha (@VeronicaRochaLA) February 14, 2018
https://t.co/chBraytByo
Television footage showed police putting a person in the back of a police car outside the high school.
Broward County Superintendent Robert Runcie said: "There are numerous fatalities. It is a horrific situation."
He added: "It is a horrible day for us."
The Florida school shooter is about 18 years old, is not a current student and was arrested without incident off campus, The Broward County Sheriff's Office has said.
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
Update 9.30pm: Florida high school shooting: Authorities say at least 14 injured
At least 14 people have been injured in a shooting at a Florida high school, US authorities said.
The shooter is in custody, Broward County Sheriff's Office said, after Swat teams swarmed Marjory Stoneman Douglas High School in Parkland.
Television footage showed police putting a person in the back of a police car outside the high school.
It followed scenes of students frantically running from the building and ambulance crews treating people outside the school on Wednesday afternoon.
Broward Sheriff's Office said on Twitter: "So far we have at least 14 victims.
"Victims have been and continue to be transported to Broward Health Medical Center and Broward Health North hospital."
So far we have at least 14 victims. Victims have been and continue to be transported to Broward Health Medical Center and Broward Health North hospital. #StonemanShooting
— Broward Sheriff (@browardsheriff) February 14, 2018
Earlier: 8.34pm: Florida high school in lockdown after shooting
A Florida high school has been locked down after a shooting, US authorities said.
The shooting happened at Marjory Stoneman Douglas High School in Parkland, according to the Broward Sheriff's Office.
It was not immediately clear how many people were wounded.
Coral Springs Police said on Twitter the school was locked down and that students and teachers inside should remain barricaded until police reach them.
Police are working an active shooter scene, and ask that if you are in touch with your student you ask that they remain calm and barricaded until police come to their room, this is for everyone's safety. Do NOT call our 911 or non-emergency number unless it is an emergency.
— Coral Springs Police (@CoralSpringsPD) February 14, 2018
TV footage showed at least one person being wheeled to an ambulance while emergency workers appeared to be helping others on the pavement.
The news broadcasts also showed students running across the street.
Len Murray's 17-year-old son, who attends the South Florida high school where shooting was reported, sent his parents a chilling text: "Mom and Dad, there have been shots fired on campus at school. There are police sirens outside. I'm in the auditorium and the doors are locked."
Those words came at 2.30pm local time on Wednesday. A few minutes later, he texted again: "I'm fine."
Mr Murray raced to the school only to be stopped by authorities under an overpass within view of the school buildings in Parkland.
No information was immediately given to parents, Mr Murray said. And he said he remained worried for all those inside.
"I'm scared for the other parents here. You can see the concern in everybody's faces. Everybody is asking, 'Have you hard from your child yet?'"