Authorities say a former student opened fire with a semiautomatic rifle at a Florida high school just as classes were ending Wednesday afternoon, killing at least 17 people.
It was the country's deadliest school shooting since a gunman attacked students and teachers at the Sandy Hook Elementary School in Newtown, Connecticut in 2012.
The shooter had a gas mask and smoke grenades when he set off a fire alarm to draw students out of their classrooms shortly before the school day ended, officials said.
As students of Marjory Stoneman Douglas High School ran out into the surrounding streets, SWAT team members advanced on the building.
Broward County Sheriff Scott Israel said the shooter was outside and inside the school at points during the attack. He told reporters that authorities found 12 people dead in the building and two more dead just outside the school and one more in a nearby street.
Israel said two other people died later under medical treatment.
Sixteen other people were wounded in the shooting and are being treated at area hospitals.
The sheriff said the suspect has been identified as Nicholas Cruz, a 19-year-old former student of the high school, who had been expelled for disciplinary reasons. He said Cruz was checked out at a hospital after his arrest and is now being held at a secure location in a public building.
Cruz was taken into custody without incident off campus about an hour after law enforcement officials arrived at the school. He had at least one rifle and multiple magazines, authorities said.
The school is located in the South Florida community of Parkland, about 45 miles north of downtown Miami. It is one of the largest in the county with more than 3,000 students.
As frantic parents rushed to the school, video from live television showed first responders treating people on sidewalks.
The sheriff's office tweeted Wednesday afternoon that "so far we have at least 14 victims." The tweet added: "Victims have been and continue to be transported to Broward Health Medical Center and Broward Health North hospital."
Broward County Schools Superintendent Robert Runcie said there were "numerous fatalities."
It is a horrific situation." He added, "It is a horrible day for us."
Live video showed SWAT team members wearing military-type fatigues with weapons at-the-ready entering the school. After the officers entered the building, dozens of students quickly exited the facility as a police officer waved them on.
The Broward Schools department said on its website that students and staff heard what sounded like gunfire and the school immediately went on lockdown.
PHOTO: "Still locked in," Marjory Stoneman Douglas High School student says in tweet, sharing image from classroom as authorities respond to shooting on Parkland, Florida, campus https://t.co/1Y5NBGZMdE pic.twitter.com/WwUhJW9mFd
— CBS News (@CBSNews) February 14, 2018
Beth Feingold told The Associated Press her daughter, Brittani, sent a text at 2:32 p.m. that said, "We're on code red. I'm fine," but sent another text shortly afterward saying, "Mom, I'm so scared."
Brittani later was able to escape the school.
President Donald Trump tweeted his condolences.
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.
— Donald J. Trump (@realDonaldTrump) February 14, 2018
Spokeswoman Sarah Huckabee Sanders told reporters Trump has offered Florida federal assistance if needed. The homeland security secretary has also been in touch with state and local officials.
"We continue to keep the victims, and their friends and family, in our thoughts and prayers," Sanders said.
Sen. Marco Rubio, R-FL, says he is "devastated and saddened" by the deadly shooting attack on a high school in his state.
The Republican senator says he remains ready to assist state and local officials and "anyone impacted by this horrible tragedy."
He also said in a statement Wednesday that he hopes authorities can find out in coming hours and days more about why and how the killer "carried out this carnage."
US Rep. Debbie Wasserman-Schultz, D-FL, also sent her condolences. She called the attack in Parkland, Florida, "another senseless school shooting ... this time in our community."
School officials have announced the school will remain closed the rest of the week.