UPDATE: Ian David Long, 28, was identified by police Thursday morning as the gunman who killed 12 people in a California bar shooting the night before.

Police said 13 people are dead after a gunman opened fire in a crowded Southern California bar late Wednesday.

Hundreds of people were inside Borderline Bar & Grill in Thousand Oaks for a country music night event when shots rang out at around 11:20 p.m. The shooter was dead inside the bar, police said. It was unclear how he died.

Witness Teylor Whittler, 19, told Fox News she was on the dance floor when she heard gunshots. She turned to see a "taller man with a gun shooting multiple people."

"We all just kind of froze for a second. And then everyone booked it and dove to the floor," Whittler said. "After the first round, it was quiet for about five seconds. And then some guys that were next to me on the floor got up and started sprinting to the back door and yelled at everyone, 'Get up! Run! He's coming!'"

She said dozens of people rushed for the door all at once, and she was caught in a "dogpile" the floor and tramped by several fleeing people.

As she tried to get up, she was struck in the head by a bar stool that someone had thrown at a window.

"At that moment, I didn't know whether I was going to be able to get up or not, and if that guy was really coming, what was going to happen to me. I was thinking that I'd go under a table until this man came up from behind me and grabbed me by the waist and pulled me up, and he told me, 'Run! Get Out! Let's go!'"

Whittler said she went to the bar with 11 friends and so far they've only been able to find six of them.

"The only thing going through my head the entire time was: Get out. You've gotta get out. Get safe."

Whittler said she was born into a military family and she's been around guns her entire life, and she said the gunman "looked like he knew what he was doing."

"He had practiced. He had been shooting before," Whittler said, identifying the weapon used as a black semi-automatic pistol.

Watch the interview above, and stay with Fox News Channel for up-to-the-minute coverage.

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