A former student opened fire with a semi-automatic rifle at a Florida high school Wednesday, killing at least 17 people and sending hundreds of students fleeing into the streets in the nation's deadliest school shooting since a gunman attacked an elementary school in Newtown, Connecticut.
The shooter, who was equipped with a gas mask and smoke grenades, opener fire on one of the state's largest schools, officials said.
Nikolas Cruz, 19, was arrested Wednesday and charged Thursday morning with 17 counts of murder. Authorities have offered no immediate details on any possible motive, except to say that Cruz had been kicked out of the school, which has about 3,000 students.
Broward County Sheriff Scott Israel said the suspect was expelled from the school "for disciplinary reasons," and that Cruz had an AR-15 and multiple magazines in his possession.
Broward County Schools superintendent Robert Runcie told reporters on Thursday that Cruz did not set off the school's fire alarms as originally thought - instead, it was the powder and smoke from the guns that set them off.
The suspect was taken into custody without resistance a mile away from the scene of the shooting. Investigators later learned the suspect had concealed himself in the crowd and was among those running out of the school.
He was wearing what appeared to be a Junior Reserve Officers' Training Corps shirt from the school with an eagle logo on the arm. Students told NBC Miami that Cruz was a part of the JROTC when he attended the school.
Twelve of the victims were found dead inside the school. One of the victims has been identified as the school's football coach, Israel said.
The sheriff said they've begun to investigate the suspect's social media and described it as "very disturbing."
He called the shooting a "horrific, homicidal and detestable act."
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Five of the victims are in critical condition, said Benny Menendez, chief medical director at the Emergency Department of Broward Health North.
"Most of the victims we've had here have had gunshot wounds," Menendez said.
Multiple students confirmed that there was a fire drill early in the morning, and when the fire alarm rang again later in the afternoon, "no one expected anything that was gonna happen," one student told NBC 6.
School board officials said staff and students heard what sounded like gunfire shortly before dismissal and the school went on an immediate lockdown.
Footage posted on social media showed students cowering under desks in one classroom as gunshots rang out.
NBC 6 spoke to the older brother of one student, who said his sister, a sophomore, was safe but “trembling in shock” at the scene unfolding at her high school.
“It’s just complete chaos out there,” he said a short distance from the school. “She was numb.”
NBC 6 also spoke with a father who was able to communicate with his child inside the school. "I'm relieved that [the suspect] has been captured, at least that part of its over. The stress from this is too much." He said his child is safe.
"This is just the worst kind of tragedy," said U.S. Rep. Ted Deutch, who represents the district that includes parts of Parkland. "It's a great community and it's just so awful to see the images coming out of there."
The school will remain closed for the rest of the week, and all school activities have been canceled, Broward City Public Schools tweeted.
Broward School Superintendent Robert Runcie said Wednesday night that grief counselors will be available at locations across the area for students, staff and families.
A prayer vigil will be held on Thursday at 2:35 p.m. at Pine Trails Park. All are invited to attend.
Another vigil is being held at noon on Thursday at the Parkridge Church.
The FBI is asking the public for information related to the shooting. Anyone with information on this incident can submit it directly to the FBI by clicking here.
Check back with NBC 6 for updates.