Updated Thursday am
A gunman 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 Nikolas 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."
The White House cancelled its daily press briefing following the news and President Donald Trump has spoken with Florida governor Rick Scott.
The president tweeted: "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."
Parent John Obin said his son, a student at the school, was in class when he heard several shots.
The father said his son advised that teachers quickly rushed students out of the school.
"This is a really good school, and now it's like a war zone," Mr Obin said.
Coral Springs Police said earlier on Twitter that the school had been locked down and that students and teachers inside should remain barricaded until police reached them.
Outside, television footage showed two people on stretchers and another person being treated on the ground near the school.
Paramedics were treating those who appeared to be students with injuries.
Len Murray, whose 17-year-old son attends the school, was stopped by authorities within view of the building.
He said: "I'm scared for the other parents here. You can see the concern in everybody's faces.
"Everybody is asking: 'Have you heard from your child yet?'"