A gunman opened fire at a Florida high school on Wednesday afternoon, February 14 killing multiple people, officials said.

The Broward County Sheriff's Office tweeted that there were "at least 14 victims" after the shooting at Marjory Stoneman Douglas High School in Parkland. It was not immediately clear how many of those victims were injured and how many had died.

But Sen. Bill Nelson, D-Fla., citing Broward County officials, told NBC News that there were "a number of fatalities."

"This is a really bad day," the senator said.

What we know so far:

•    "At least 14 victims," according to the Broward County Sheriff's Office

•    A suspect is in custody

•    The shooting at Marjory Stoneman Douglas High School in Parkland started around 2:30 p.m. ET on Wednesday.

Authorities responded to an active shooter situation around 2:30 p.m., and for over an hour, said that the gunman was not in custody. Broward County Sheriff's Office announced on Twitter just after 4 p.m. that a suspect had been apprehended, adding that the scene was still active.

The high school went on immediate lockdown, Parkland Mayor Christine Hunschofsky told NBC Miami. She did not have details on casualties or who the shooter was.

"It’s sad. It’s sad that these tragedies happen in our country," she said. "Many of the students have been in touch with their parents. We have many, many parents out here."

Parents told the station that students were hiding inside closets at the school and that teachers had told them not to leave the building.

Joel Leffler, who has a son and a daughter at the school, said both of his children were safe but in shock.

"My son called me as it was unfolding, running. He had to jump a fence," Leffler told NBC News. "My son heard around eight gunshots as he was running out."

When he reached his daughter, she was whispering, he said.

"My daughter, who was there in the freshman hall where the shooting took place — she's in shock right now, and she's being taken out by SWAT," Leffler said. "She saw multiple dead bodies."

Source: NBC News