The suspect, Nikolas Cruz, 19 – a former student of Marjory Stoneman Douglas High School – is in custody, the sheriff said.
Cruz was expelled for unspecified disciplinary reasons, and police are investigating his digital profile, Israel said.
He said: “He got expelled for disciplinary reasons, I don’t know the specifics.”
“We are beginning to dissect his websites and things on social media that he was on and some of the things that have come to light are very, very disturbing.
“It’s a horrific, horrific day,” Israel said. “Just pray for this city. Pray for this school, the parents, the folks that lost their lives.”
Seventeen people, including the suspect, were sent to area hospitals, said Dr. Evan Boyar of Broward Health. The suspect was treated and released to police.
The victims included students and adults, the sheriff said. Twelve were killed inside the building and two died outside, he said. One died in the street and two died at the hospital, Israel said.
Melissa Falkowski, a teacher at the high school, has been speaking to CNN about the shocking events of the day.
“Drills for a code red (active shooter) situation had been well rehearsed,” she said.
We could not have been more prepared for this situation … we have trained for this, we have trained the kids for what to do …
We did everything that we were supposed to do.
I feel today like our government, our country, has failed us and failed our kids and didn’t keep us safe.”
Falkowski detailed what happened when the fire alarm went off on Wednesday afternoon – the second of the day after a drill in the morning:
“It was fourth period … I was working with the kids, making the school newspaper, when the fire alarm went off.
We just followed the protocol: when the fire alarm goes off, we have to evacuate.
We make it out of my room into the hallway … the security guard posted in our area said no, it’s a code red, go back.
We were yelling at kids in the hallway to go back, to go inside.”
She said she and 19 students huddled in a closet while the shooting unfolded around them.
“I just tried to keep them calm, tell them everything is going to be OK, just hold them together. You just do the best you can for the kids that you’re supposed to keep safe.”
Falkowski said her own students are safe, but she does not yet know which of her colleagues and other students have been killed or injured.