There are “multiple fatalities” from a shooting at a South Florida high school on Wednesday — and the suspected gunman, a former student, is in custody, according to authorities and reports.

The death and injury count at the Marjory Stoneman Douglas HS in Parkland, near Fort Lauderdale was not immediately known.

The suspected gunman is a 19-year-old who “may have been identified as a potential threat to fellow students in the past,” a teacher told the Miami Herald

A law enforcement source identified the ex-student as Nikolas Cruz, the Herald reported.

“We were told last year that he wasn’t allowed on campus with a backpack on him,” math teacher Jim Gard told the paper.

He said Cruz was in his class last year.

“There were problems with him last year threatening students, and I guess he was asked to leave campus,” he added.

“I don’t know why he left, I don’t know when he left,” Broward County Sheriff Scott Israel told reporters of the shooter, who he said “was taken under arrest without incident.”

Israel, who was speaking at 5 p.m., said there were multiple fatalities, and that 14 people had been transported to area hospitals.

He said that SWAT teams had yet to clear the school building. After that, first responders would search for any additional casualties, he said.

The US Coast Guard and Palm Beach County sent helicopters to help with medical evacuations, The Margate Fire Department told the CBS affiliate in Miami.

“There are numerous fatalities,” the superintendent of Broward County schools, Robert Runcie, told reporters, his voice breaking.

“It’s a horrific situation. It’s just a horrible day for us.”

There is no indication of more than one shooter, and it is believed that one of those killed is “an administrator” at the school, he said.

“It’s a day that you pray every day you’ll never have to see,” he said.

CBS 4 Miami texted with a student who was hiding in a closet.

“All of a sudden there was a really loud noise… people are crying in the closet,” the student wrote to CBS 4.

The outlet reported a number of people could be seen from their newscopter being loaded into ambulances on a stretcher.

Coral Springs police advised students and teachers in the locked-down school to remain barricaded until officers reach them.

Real-time news footage from the scene included the all-too-familiar images of parking lot triage operations, of worried waiting parents and of dozens of kids running from the school with their hands in the air or on the shoulders of their fellow students.

The shooting happened at around 2:30 p.m., close to dismissal time.

“Kids were running out full of blood,” Derval Walton, whose 15-year-old daughter is a freshman at the school, told the Sun Sentinel.

“Kids were falling in the grass.”

Hannah Siren, 14, was in math class on the third floor.

“The people next door to us must have not locked their door,” she told the paper, breaking into tears. “They all got shot”

Asked how many, she answered, “10 or … seven.”

President Trump tweeted his “prayers and condolences to the families of the victims.”

“No child, teacher or anyone else should ever feel unsafe in an American school,” he tweeted, adding that “We are working closely with law enforcement on the terrible Florida school shooting.

The White House issued this statement:

“The President has spoken with Governor Scott of Florida and offered federal assistance if needed.

“Department of Homeland Security Secretary Nielsen also spoke with Governor Scott as well as state and local officials. She has briefed the President on those conversations.

“The Governor, the Secretary, and other Administration officials will continue to keep the President updated… We continue to keep the victims, and their friends and family, in our thoughts and prayers.”

First lady Melania Trump tweeted, “My heart is heavy over the school shooting in Florida. Keeping all affected in my thoughts & prayers.