Teachers at the Marjory Stoneman Douglas High School in Florida took part in an ‘active shooter drill’ just hours before the mass shooting on Wednesday. 

Earlier on in the day, teachers were told there would soon be a “code red” or “lockdown” drill – in which teachers and students would “practise” their response to a mass shooting.

Miamiherald.com reports: When the fire alarm rang near the end of the school day on Wednesday, teacher Ernest Rospierski assumed it was a “code red” drill.

Rospierski was sitting at his desk around 2:25 p.m. when the fire alarm rang. His students filed out of their third-floor classroom and made their way toward the stairs. Then Rospierski heard the sound of gunfire.

“Turn around, go to your classrooms!” he yelled to the students.

Students started running back toward Rospierski and he tried to steer them into open classrooms. By the time Rospierski got to his classroom door, the shooter was at the end of the hallway.

Rospierski was locked out of his classroom, so he pushed eight kids into a two-and-a-half foot alcove by the classroom door. He desperately tried to keep the students out of the line of fire. Rospierski saw the shooter approach wearing a helmet and a mask. He didn’t know it at the time, but the gunman was a former student who had been in Rospierski’s freshman World Geography class five years ago.

Then Rospierski felt a bullet graze his cheek.

The shooting stopped abruptly as the gunman reloaded. Rospierski said he took advantage of the pause to push his students toward the stairway so they could escape. He followed closely behind. A girl was lying by the stairs. He checked for a pulse but couldn’t find one.

Then the shooting started again. With his students safely on their way down the stairs, Rospierski ran into the bathroom to hide. He was there for what felt like 20 or 25 minutes before police arrived. For those harrowing minutes, Rospierski said he thought about his wife, Andrea Kowalski-Rospierski, who also teaches at the school and was in another building across campus.

“My biggest concern wasn’t for me, it was for my wife more than anything else,” he said.

When police finally arrived, they escorted Rospierski out of the building. As they went through the first floor, the teacher saw carnage everywhere.

Outside the school, a police officer questioned Rospierski about what he’d seen. Then the teacher went across the street, where at last he was able to call his family and tell them he was all right. Mercifully, his wife was unharmed.

When Rospierski learned that law enforcement had identified the suspect as 19-year-old Nikolas Cruz, he realized the gunman was a former student. Cruz hadn’t caused problems in Rospierski’s class, but the teacher remembered that he’d had discipline problems in other classes.

Rospierski said it appeared that Cruz had taken steps to ensure as much carnage as possible — as of Wednesday night, the death toll was 17, with 15 more reported wounded. Of all the buildings on campus, he had picked the only one with interior hallways. The 1200 building largely houses ninth-graders. The other buildings on campus have exterior walkways, Rospierski said.

“He picked bad person 101 very well because he picked the one contained building, and then he pulled the fire alarm,” the teacher said.