MURRIETA, Calif. (KABC) -- Like many people at the Route 91 Harvest Festival concert that night, Liz Moreno didn't think it was gunfire.
"We heard a couple of what we thought were fireworks," said Moreno.
But when the performers at the concert in Las Vegas on Oct. 1, 2017 began running off the stage, and she began to see the horror unfold all around her, Moreno said she knew it was real.
"We turned around and I saw a lady behind us was shot in the face," said Moreno. "And then I told my boyfriend, as soon as this stops, I'm running, we need to get out of here."
Fifty-eight people were killed and hundreds more injured in the deadliest mass shooting committed by one person in U.S. history. But Moreno and her boyfriend were able to get out unharmed. Moreno credits an active shooter survival training class she attended a couple of years ago.
"I never thought I would use it," she said. "It just came back."
Moreno said the class was given to her coworkers in Murrieta. She said she really didn't give it much thought over the past couple years. Some of what she learned in that class came right back to her.
"Even if you don't process all of it, it's going to be in your brain," said Moreno. "And if three years down the road, it's in there, and it came back, and I'll help you."
The class was taught by Michael Julian, who is also a private investigator and security specialist. It's called the A.L.I.V.E. Active Shooter Survival program.
"A.L.I.V.E. stands for assess, leave, impede, violence and expose," said Julian. "If you can stay alive for 10 minutes, your chances of surviving an active shooter event increase exponentially."
Julian said one of the worst things you can do in an active-shooter situation is freeze. But he said a lot of people do.
"Roosevelt said the best thing you can do is the right thing, and the next best thing is the wrong thing," said Julian. "(But) the worst thing is nothing. You have to do something."
"Just seconds could have (made things) come out different for us," said Moreno, who often wonders if things would have turned out differently if she hadn't taken Julian's class.
Las Vegas shooting survivor credits active-shooter survival training with escape
More TOP STORIES News