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LAS VEGAS (CBSMiami) – At least 59 people were killed and more than 500 were injured when a gunman opened fire on a crowd at the Route 91 Harvest country music festival on the Las Vegas Strip making it the deadliest mass shooting in modern U.S. history.

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Country singer Jason Aldean was on stage at the time when witnesses heard what sounded like rapid machine gun fire.

“And then we saw Jason run off stage and people all over the grassy area in front of the stage were just some were falling some were screaming and running and yelling,” said one woman.

Concert-goers reported seeing muzzle flashes from the upper floors on the nearby Mandalay Bay Hotel and Casino, and the sound of what they described as automatic gunfire.

“Everybody started screaming and started to run, and I looked over to my right. This girl had been standing right beside me and she had fallen. First she stood there and she grabbed her stomach. She looked at her hands, her hands were all bloody. She was wearing a little crop top and blue jean shorts and cowboy boots. She looked at her hands, her hands were all bloody and she just screamed and fell down,” said Gayle Davis. “Everybody started yelling, some guys there. And we just started jumping up and down waving for help, for help, and then all of a sudden we heard a whole bunch of shots fired and people started running.”

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The sole gunman, identified as 64-year-old Stephen Paddock, was found dead by police in a room on the 32nd floor of the hotel. Police said he had made holes in the windows so he could fire down into the crowd of about 22,000 people.

“We believe the individual killed himself prior to our entry,” said Clark County Sheriff Joe Lombardo.

Assistant Clark County Sheriff Todd Fasulo said officers have found 23 firearms.

Officials added that Paddock had two “bump-stocks” that could have converted semi-automatic firearms into fully automatic ones.

The devices have attracted scrutiny in recent years from authorities.

California Sen. Dianne Feinstein has long railed against them. Several years ago, she told The Associated Press she was concerned about the emergence of new technologies that could retrofit firearms to make them fully automatic.

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“This replacement shoulder stock turns a semi-automatic rifle into a weapon that can fire at a rate of 400 to 800 rounds per minute,” she said.

Paddock lived in a retirement community in Mesquite, Nevada about 90 minutes outside of Las Vegas. Investigators searched his home, finding 19 firearms, thousands of rounds of ammunition and explosives.

Authorities said they had no contact with Paddock before the shooting.

“We believe it’s a solo actor. A lone wolf,” without any militant links, said Lombardo.

Police have yet to determine a motive.

Lombardo said they were able to locate Paddock’s girlfriend, identified as 62-year-old Marylou Danley, who was sought after the shooting.

“We have located her out of the country, we believe her, at this time, not to be involved,” said Lombardo.

Marylou Danley (Source: Las Vegas Police)

An off-duty police officer attending the concert was killed, Lombardo said. Two on duty officers were among the injured, one was in critical condition.

A brother of the suspect says Stephen Paddock was “not a normal guy” and frequently played high stakes video poker. Eric Paddock in an interview in Orlando said his brother once “texted me a picture that he won $40,000 on a slot machine.”  Eric Paddock says he last had contact with him via text messages in September. He says his brother being named by authorities as the shooting suspect was “like if an asteroid fell out of the sky.”

President Donald Trump called the mass shooting attack in Las Vegas “an act of pure evil.” He will travel to Las Vegas on Wednesday to meet with law enforcement.

The shooting rocked the country music world and both Aldean, and Jake Owen who performed before him, took to social media to express just how stunned and saddened they were by what had happened.

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In an odd twist Monday afternoon, it was learned Stephen Paddock’s father was a notorious bank robber who tried to run down an FBI agent with his car in Las Vegas in 1960 and was on the agency’s most wanted list after escaping from a federal prison in Texas in 1968.