PARKLAND, Fla. (WFLA) – Seventeen people were killed when an active shooter opened fire at Marjory Stoneman Douglas High School in South Florida, according to Broward County Sheriff Scott Israel.

The suspect in custody was identified as 19-year-old Nikolas Cruz, a former student at the school, The Associated Press reported.

The sheriff said Cruz was expelled from the school for disciplinary reasons.

According to Sheriff Israel, Cruz had countless magazines and one AR-15.

The agency said 12 of the victims were killed inside the building, two were killed outside and another person was killed on the street.  Two of the victims died at the hospital.

The sheriff said in a press conference Wednesday evening that 12 of the 17 killed have been identified. All students in the school have been accounted for.

Seventeen others were taken to area hospitals following the shooting, according to reports.  Three of those people are listed in critical condition.

“It is a horrific, homicidal, detestable act,” the sheriff said. He said he would not elaborate on the number of deaths until an all clear is given. Officials aren’t sure if some people are still hiding or injured inside. SWAT is going building to building.

The Broward sheriff said that the parent staging area is at the Marriott 11775 Heron Bay Boulevard in Coral Springs.

The sheriff said Cruz had been inside and outside the school buildings. He tried to blend in with other students walking away from the school and was arrested along a nearby street.

Cruz was seen being put into a police cruiser at about 4 p.m., and about 20 minutes later, he was removed from the car, put onto a stretcher and taken to a local hospital.

A father said Cruz pulled a fire alarm at the school and that caused students and teachers to come out of their classroom so he could start shooting in the hallway. The students already had a fire drill earlier in the day.

“It was supposed to be just a fire drill, we thought it was just a fire drill because we had one earlier. But as soon as the fire drill got pulled — the fire alarm got pulled — the kids were evacuating, I heard five pops. And I was like, that’s not a drill because we never did a drill like that. When we started evacuating towards the back of Wesley’s with the middle school I knew that it was more than a drill because we’d never done that. I graduated and I came back to visit one of my teachers,” said a former student.

Reports said Cruz currently goes to an alternative school.

“Honestly, a lot of people were saying that it was gonna be him, stuff like that. We actually, we – a lot of kids threw jokes around like that saying that he was going to be the one to shoot up the school. It turns out, everyone predicted it.”

“Yeah, he was on the third floor. He knows the school layout. He knows where everyone would be at as of right now. He’s been at the fire drills. He’s prepared for this.stuff,” a student said.

Officers responded to Marjory Stoneman Douglas High School at 5901 Pine Island Road in Parkland at about 2:30 p.m.

School board officials said staff and students heard what sounded like gunfire shortly before dismissal, and the school went on an immediate lockdown.

Video showed dozens of officers and ambulances at the school as students ran out. Some reported victims were seen being carried out of the school.

Students were escorted by armed police out of the high school in a single file. Parents said their kids were trapped inside.

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.”

ATF agents from the Miami Field Division responded to the school.

President Donald Trump and Florida Gov. Rick Scott were notified of the situation. Scott is traveling to Broward County now to be briefed by emergency management officials and law enforcement.

“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,” Trump tweeted.

In a press conference Wednesday night, Florida Attorney General Pam Bondi said the state will pay for funerals of those killed and also pay for counseling for survivors.

Broward County Superintendent says it appears to be the deadliest school shooting in Broward County’s history.

“This is a really bad day for Florida and for the country,” Nelson said.An official GoFundMe campaign has been created by the Broward Education Foundation. The funds raised will be used to provide direct relief and financial support to the victims and families following the shooting in Florida.