PARKLAND, Fla. – 15 February 2015: A former student at a Florida high school opened fire in the school on Wednesday, causing "numerous fatalities" and sending hundreds of panicked young people fleeing their classrooms before he was arrested by police, authorities said.

The Broward County Sheriff's Department said "at least 14 victims" from the shooting had been taken to area hospitals, but it was not immediately clear how many of those survived and how many may have died of their injuries.

Sheriff Scott Israel told reporters a short time later there were "multiple" deaths.

CNN reported 16 people were killed, a figure that could not be independently confirmed

The violence erupted shortly before dismissal at Marjory Stoneman Douglas High School in Parkland, about 45 miles (72 km) north of Miami. Live television footage showed students streaming out of the building as dozens of police and emergency services personnel swarmed the area.

"There are numerous fatalities. It's a horrific situation," Broward Country Schools Superintendent Robert Runcie told reporters.

The gunman, believed to be about 18 years old, surrendered to police without a struggle, Israel said.

"It's catastrophic," he said. "There really are no words."

Israel offered few details on the suspect's identity or motive other than to say he had previously attended the school. "I don't know why he left, I don't know when he left," the sheriff added.

It was the 18th shooting in a U.S. school so far this year, according to gun control group Everytown for Gun Safety. That tally includes suicides and incidents when no one was injured, as well as the January incident when a 15-year-old gunman killed two students at a Benton, Kentucky, high school.

More than five years have passed since a gunman killed 20 first graders and six educators in Newtown, Connecticut, stirring the long U.S. debate about gun rights, which are protected by the Second Amendment of the U.S. Constitution.

SCENES OF FEAR

Staff and students told local media that a fire alarm went off around the time the shooting started, sparking chaos as some 3,000 students at the school first headed into hallways before teachers herded them back into classrooms, to seek shelter in closets.

Kyle Yeoward, a 16-year-old junior, told Reuters he was in the bathroom on the second floor of the building on the campus where most of the shooting took place, when he heard two shots.

"He let loose on the freshman building," Yeoward said.

McKenzie Hartley, 19, who identified herself as the sister of a student at the school described the scene in a text message to Reuters: "She heard him shooting through the windows of classrooms and two students were shot."

Panicked parents checked on their children.

"It is just absolutely horrifying. I can't believe this is happening," Lissette Rozenblat, whose daughter goes to the school, told CNN. Her daughter called her to say she was safe but the student also told her mother she heard the cries of a person who was shot.

"She was very nervous. She said that she could hear the person who was shot crying out for help," she said.

Televised images showed dozens of students, their arms in the air, weaving their way between law enforcement officers with heavy weapons and helmets, and large numbers of emergency vehicles including police cars, ambulances and fire trucks.

The school had recently held a meeting to discuss what to do in such an attack, Ryan Gott, a 15-year-old freshman told CNN.

"My prayers and condolences to the families of the victims of the terrible Florida shooting," U.S. President Donald Trump said on Twitter. "No child, teacher or anyone else should ever feel unsafe in an American school."