Senior David Hogg told Eyewitness News he thought he heard a gunshot during his afternoon class, but that was immediately followed by a fire alarm.
As students filed into the hallway, they were only feet away from the makings of a horrific school shooting.
"After I started running with the people, I realized that wasn't the best choice because there was a janitor that thank God stopped me and all of my fellow students from going in that direction, towards the shooter," Hogg said.
Hogg and his classmates turned around, but needed a place to hide. That is when a teacher ran to open her classroom door.
"Without her, who knows how many of us would have died, 'cause we were easily 100 feet away from the freshman building, and again, we thought this was a drill," Hogg said.
Florida janitor risked his life to save students
Hogg explained he's having a hard time processing all of this, his fortunate escape, but also how many of his fellow students did not survive.
He wanted everybody who is watching to hear one message:
"We cannot let this happen again."
WATCH: What students saw inside Douglas HS
Douglas HS student describes massacre scene