'The shots just kept coming': Eyewitnesses describe the harrowing scene after a gunman opened fire at a Las Vegas festival

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Las Vegas concertgoers.

What was meant to be a fun evening spent listening to live country music on the Las Vegas strip turned into a nightmare when a gunman opened fire on concertgoers Sunday night.

Stephen Paddock, the 64-year-old man police have identified as the shooter, fired off several rounds from what appeared to be an automatic rifle, killing more 58 and injuring over 500 in the deadliest mass shooting in modern US history.

Several witnesses initially mistook Paddock's gunfire for fireworks.

Carly Krygier, a woman who attended the concert with her 4-year-old daughter, told CNN on Monday morning, "We just heard what we thought were fireworks. It took everybody a couple of seconds to realize that it wasn't."

"That's when everybody just started yelling, 'Get down!'" Krygier said, adding that she immediately "put the baby on the ground and got on top of her."

Another concertgoer, Amanda Mattoon, told NBC Los Angeles that she heard "three pops" at first.

"We thought it was a cap gun or fireworks or something, and then they started clearing the stage," Mattoon said. "All the performers started running and everyone started dropping on the ground, and shots just kept going and going and going."

Las Vegas police said Paddock was found dead in his hotel room when they entered following the shooting, possibly as a result of suicide. They discovered at least 10 rifles in his hotel room, said Joseph Lombardo, the sheriff of the Las Vegas Metropolitan Police Department.

Eric Paddock, the shooter's brother, told CBS News that Stephen was "not an avid gun guy at all."

"The fact that he had those kind of weapons is ... just... where the hell did he get automatic weapons? He has no military background or anything like that," Eric Paddock said.

"Bullets flying everywhere," one witness told KSNV-TV of the shooting. "Everybody running. It was really bad."

The bullets "were ricocheting everywhere," the witness said. "They were firing from somewhere high, and they were unloading clip after clip after clip after clip."

"It was hundreds of shots," he told the Las Vegas NBC affiliate. "It wasn't 'sounded like.' It was hundreds of shots."

Paddock was retired and had no criminal record before the attack, Reuters reports. A Washington Post report described Paddock as a quiet man who occasionally came to Las Vegas to gamble or catch concerts, was a former resident of Texas, and held a hunting license in Alaska.

Police said he checked into his Mandalay Bay hotel room with his girlfriend's identification three days before the attack. Police initially identified her as a person of interest but have said she is not a suspect in the attack.

REUTERS/Las Vegas Sun/Steve Marcus

A pair of cowboy boots is shown in the street outside the concert venue on the Las Vegas Strip October 1, 2017.

One woman who attended the concert with her husband and their friends told CNN on Sunday night that as Paddock began firing, "everyone was just, like, literally laying on top of each other trying to get out of the way."

"And the shots just kept coming," she said. The woman added that when everybody ducked for cover, she and her friends saw a man who had been shot who was bloody and unconscious.

She said that after helping the man who had been injured and getting away from the scene of the shooting, she and her husband discovered that people were hiding underneath their car for cover.

"There was a gentleman that was shot, and he said, 'Can you help me?'" she recalled to CNN. "And so I put him in my car, and I had, like, six people in my car. People without shoes, running just to get away."

The Instagram star and professional poker player Dan Bilzerian was caught up in the shooting, as well.

In multiple Instagram stories filmed while fleeing the attack, Bilzerian described scenes of chaos and said he saw someone next to him get shot.

"F---, this girl just got shot in the f---ing head," Bilzerian told his 23 million followers in the first post, which was uploaded around 10 p.m. PDT. "So f---ing crazy."

"So I had to go grab a gun. I'm f---ing headed back. It's f---ing so crazy - some kind of mass shooting," he said in the second video, which was broadcast about an hour later. "F---ing guy had a heavy caliber or whatever."

"Saw a girl got f---ing shot in the face right next to me," he said before the clip cut out.

The Daily Mail quoted Paddock's brother Eric as saying he and his mother were "in shock" and "dumbfounded" after finding out about the shooting. According to the Daily Mail, Eric Paddock described his brother as a normal guy who must have "snapped."

The police are not investigating the attack as an act of terrorism at this time.

Families looking to locate missing loved ones can call 1-866-535-5654.

Alex Lockie and Alexandra Ma contributed reporting.