The suspect accused of committing a deadly shooting at a local high school in Parkland, Florida, has been named by US media.
Nicolas Cruz, 19, was named in various media reports. Police previously said that Cruz had been a former student.
Officials have warned that the scene at Stoneman Douglas High School “is still active”.
School superintendent Robert Runcie told reporters: “there are fatalities involved here.”
Both Mr Runcie and the Sherriff, Scott Israel, said the suspect is a former student of the school.
“So far we have at least 14 victims,” the Sherriff’s department said, without specifying their condition.
US media outlets reported that up to 20 people may have been injured, while some have been evacuated.
A local Fox news affiliate reported seeing several people being treated for injuries outside the school.
Meanwhile, Florida Senator Bill Nelson told Fox News there were “many deaths”, citing conversations with the school superintendent, the FBI, and the undersheriff.
The local public school district tweeted: “Today, close to Marjory Stoneman Douglas High School’s dismissal, students and staff heard what sounded like gunfire.”
“The school immediately went on lockdown but is now dismissing students. We are receiving reports of possible multiple injuries,” it said.
Police were clearing students from the school “one building at a time”, the school said.
Video footage from the scene showed students being evacuated in small groups, while armed police patrolled the school’s perimeter.
As the situation unfolded, helicopter footage appeared to show a person being handcuffed and placed in the back of a police car.
Coral Springs Police department tweeted instructions to teachers and students to “remain barricaded inside until police reach you”.
The FBI also said it was attending the scene and assisting local law enforcement.
US television networks reported large numbers of parents had gathered outside the police perimeter.
Several witnesses inside the building at the time told news outlets that the fire alarm had been set off as the shooting began.
One student evacuated from the school told CBS that Miami students had thought it was a drill.
“We already had one earlier this morning… and then we heard gunshots; some students thought it was not that serious.”
Another student, Bailey Vosberg, said: “I heard what sounded like fireworks and I looked at my friend and he asked me if I heard that.”
“Immediately, I knew. I didn’t say anything to him, I just hopped over the fence and I went straight to the road that our school is located on – and as I got there there was just Swat cars and police units, police vehicles just flying by, helicopters over the top of us.”
A teacher told WSVN that she hid in a closet with 19 students for 40 minutes – and that the school had undergone training for such a situation six weeks ago.
President Donald Trump tweeted condolences “to the families of the victims”. White House Deputy Press Secretary Lindsay Walters said the president had been briefed and that the White House was monitoring the situation.
Florida Governor Rick Scott said he spoke to President Trump about the shooting, and was continuing to receive updates from law enforcement.
Congressman Ted Deutch, the district’s representative, tweeted: “I’m sick about this news from home. Just spoke with the sheriff. This is devastating.”
He said it was an “incredible school in my district – great teachers and staff, involved parents and amazing kids. Spoke with the kids there just a few weeks back.”
Students were taken by bus to a “staging area” on Heron Bay Blvd, Coral Springs, where their parents could collect them.
Wednesday’s attack is the 18th shooting in the US this year on or around school premises, according to research by Everytown for Gun Safety.
Since 2013, there have been 291 reported school shootings in America, which averages out to about one per week.
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