By Nicole Chavez, Dakin Andone and Christina Maxouris, CNN

It was a night like any other at the popular Borderline Bar and Grill in Thousand Oaks, California.

It was "college night," and people were dancing, playing pool and keeping an eye on the basketball game -- until the evening came to an abrupt and tragic end.

From across the bar, Holden Harrah saw a bearded man walk in and shoot a woman who was behind the counter.

"I see that girl every single time I'm there," he told CNN, fighting back tears. "I don't know her name, but (she) is someone I make small contact with and I say hi every time.

"I don't know if she's alive."

A gunman opened fire Wednesday night at Borderline Bar & Grill, authorities said, killing at least 12 people and injuring others in a city described by its mayor as "one of the safest" in the country.

"This guy just came out of nowhere and came out with a gun and shot people in Thousand Oaks, California," Harrah said. "And that's what's really blowing my mind, it's a really safe area.

"I'm just in shock with what I saw with my own two eyes."

'A tall, dark figure'

Taylor Von Molt, 21, was dancing when she heard what sounded like a balloon popping.

"And I was confused because we didn't have any balloons at the time," she told CNN. "And then I heard it a couple more times, and I turned around and I saw him.

"He had a black mask -- what looked like a bandana on the bottom of his face -- sunglasses, black hoodie, dark jeans," she said. "And he's kind of bigger. But kind of more burly. Scary."

Von Molt ran as gunshots rang out and tripped on her way to the exit. Others trying to escape kept running over her, but she was finally able to get up and sought refuge in a nearby apartment.

When Matt Wennestrom first heard the gunshots, he turned and saw "a tall, dark figure with a handgun opening fire on one of my closest friends."

"We saw him and we dropped down immediately, the group of five to six guys that I was with, and we covered the girls," Wennestrom said.

The group jumped up during a pause in the gunfire and began throwing stools through the bar's windows, he said.

As they were jumping out the window, he said, they heard the next round of gunshots.

Gunman 'was shooting everything'

John Hedge told CNN's Brooke Baldwin he had been hanging out at the bar with his stepdad and was just about to call it a night.

"I just remember sitting there, just like any other night," Hedge said. "You know, you play some pool and the Lakers game was on, and we were just having a good time."

But everything changed when he heard the first shots of gunfire.

"You think it's a joke and it takes a couple seconds to kick in, and then I see my stepdad on the ground, he's laying there and he's yelling at me, 'John, John, get down,' you know?"

Hedge watched as the gunman opened fire on girls hiding behind the front desk, he said, before seeking refuge in the bathroom.

Hedge just managed to escape, and ran over the body of a security guard on his way out, he said.

"Those seven, eight steps to the front door -- they couldn't have taken any longer," Hedge said.

Tim Dominguez also saw how the horrific scene unfolded.

"I looked up and he was moving to the right. He shot the doorman, bouncer ... just a young man," Dominguez told CNN affiliate KABC, choking up. "Then he shot the cashier, just a young girl."

He said the gunman said nothing at all.

Minutes after the first shots were fired, people jumped out of windows, hid in bathrooms and "dog-piled on top of each other."

A student named Summer, who was also inside the bar, said the gunman "was shooting everything, from the speakers to anything."

California Lutheran University student Teylor Whittler, 19, told KABC that people were trying to hide in silence when men ran toward a back door of the bar and warned them the gunman was coming.

As she escaped through the door, she heard a second round of shots.

"I think everyone was in so much of a shock that it was sheer panic," Whittler said.

A 'very sad scene'

Another witness told CNN she hid from the gunman in the bar's attic.

Lindsey, who asked to be identified only by her last name, saw the gunman walk in "and immediately had this feeling of knowing what he was doing," she told CNN's Kate Bolduan.

At the sound of gunfire, Lindsey dropped to the floor and began making her way to the kitchen, she said.

"And I look over, some Borderline staff they were yelling at me to get up the ladder and go up into the attic, which I thought was brilliant," she said. "I definitely owe them my life."

Police found Lindsey and the others holed up in the attic and knocked on the door, telling them it was OK to come out, she said. But she was so terrified she asked them over and over, "Are you sure? Are you sure?"

"It wasn't until I went outside and embraced my friends and my boyfriend that I knew we were safe."

On her way out of the bar, Lindsey said she saw something she never wants to remember.

"Very sad scene," she said. "I tried to put my hands over my eyes, but even just keeping my head down and walking, it's kind of inevitable to see what had happened there."

Correction: This story has been updated to attribute a witness' quotes correctly.