Las Vegas Shooting: 58 Killed and More Than 500 Hurt Near Mandalay Bay

A lone gunman released a rapid-fire barrage of bullets from the 32nd floor of a Las Vegas hotel late Sunday, killing at least 58 people and injuring more than 500 others attending a country music festival below, officials said.

It was the worst mass shooting in modern American history.

The shooter, identified by law enforcement officials as Stephen Craig Paddock, 64, of Mesquite, Nevada, fired shot after shot from his room at the Mandalay Bay Resort and Casino down on the crowd of about 22,000, sending terrified concertgoers running for their lives.

“We heard what sounded like firecrackers going off. Then all of a sudden we heard what sounded like a machine gun. People started screaming that they were hit," witness Meghan Kearney told MSNBC. "When we started running out, there were probably a couple hundred [people] on the ground.”

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She added: "People kept dropping and dropping … People were getting shot one foot away from us. People were trying to save their friends. There were gunshots everywhere. Helping them would’ve meant that we got shot, too.”

58 people were killed, more than 500 injured in deadliest mass shooting in modern American history.

Gunman identified as Stephen Paddock, a 64-year-old man from Mesquite, Nevada.

At least 10 weapons were found inside Paddock's room at the Mandalay Bay Resort and Casino.

President Trump, who will visit Las Vegas on Wednesday, called the shooting "an act of pure evil."

Police responded to reports of the shooting just after 10 p.m. (1 a.m. ET). Las Vegas Metropolitan Police Sheriff Joseph Lombardo told reporters Monday that authorities believe Paddock killed himself before police entered his room. Earlier, officials had said police fatally shot Paddock.

Authorities were digging into Paddock's history. Other than a citation he received several years ago that was "handled as a normal practice" by the courts, Lombardo said he had no criminal background.

Paddock is believed to have checked into the hotel on Sept. 28, Lombardo said, and had an "excess of 10 rifles" in his room.

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It was not clear whether Paddock had specifically requested a room on a high floor that overlooked the concert venue. Hotel employees had been in his room before the shooting and did not notice anything unusual, according to Lombardo.

Two broken windows could be seen from the 32nd floor of the hotel, curtains billowing out of them. Law enforcement officials said Paddock had connecting rooms or a suite and ran between both windows, firing out of both, either to get a different vantage point or to avoid return-fire.

They believe he smashed the windows with a something like a hammer before he started firing.

The shooting started while performer Jason Aldean was onstage. Witnesses described a chaotic scene of back-to-back bullets raining down from above, lasting for up to 10 minutes.

Fellow performer Jake Owen said he was standing about 50 feet away from Aldean when the shots started.

"It got faster and faster, almost like it was an automatic rifle," Owen said. "At that point, everyone on stage started running everywhere."

Owen dashed by victims covered in blood and eventually found shelter in his bus. The gunfire still hadn't stopped by the time he got there, he said.

"It wasn't something that was quick. It was chaos for a pure seven to 10 minutes," he said.

A map shows the area of the shooting in Las Vegas. NBC News

Flags at the White House and U.S. Capitol were lowered at half-staff on Monday. President Donald Trump said he will be visiting Las Vegas on Wednesday and called the shooting "an act of pure evil."

"Hundreds of our fellow citizens are now mourning the loss of a loved one," Trump said at a press conference. "We cannot fathom their pain. We cannot imagine their loss. To the families of the victims, we are praying for you, and we are here for you."

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The shooting is not believed to be connected to international terrorism. Authorities have not said what kinds of weapons were found.

Former Las Vegas Metropolitan Police Department Sheriff Bill Young’s 22-year-old daughter was at the concert. Young told MSNBC his daughter said the weapon “sounded like a machine gun” and that she and her friends took cover under a desk.

Live Blog: Latest Updates on the Concert Massacre

"I picked up the phone, my cellphone, and she was screaming and yelling, 'Dad, dad, dad, dad, somebody’s shooting at us, and I don’t know what to do.' She was hysterical and I tried to just calm her down," Young said. "She could hear the gun shots — sounded like a machine gun, she said — and they didn’t know where they were coming from. She had nowhere to take cover, so I told her just to run as fast as she could, as quick as she could out of the arena. Get as far away from it as she could where she thought the line of fire might be."

Related: Full Coverage on the Las Vegas Shooting

At least one off-duty Las Vegas police officer was among those shot, Lombardo said. Several other off-duty police officers are believed to be among the dead and injured.

The massacre put the normally bustling Strip at a standstill. Flights in and out of the Las Vegas airport were temporarily halted.

Police located Paddock’s roommate, Marilou Danley, 62, and don't think she was involved, Lombardo said, adding that the investigation is ongoing.

A search of their home in Mesquite, located about 80 miles away from Las Vegas, was underway.

Related: Photos Capture Chaos of Concert Massacre

The suspect's brother, Eric Paddock of Orlando, told NBC News he was "dumbfounded" by the shooting.

"He was just a guy," Eric Paddock said. "He lives in Mesquite, he went to the hotels, he gambled, he went to shows."

"We are completely at a loss," he added.

Senior law enforcement officials and a Las Vegas casino executive said Paddock had made several large gambling transactions in recent weeks, including some of more than $30,000 a day. It wasn't known if they were losses or wins.

In 2012, Paddock sued the Cosmopolitan Hotel in Las Vegas for a slip-and-fall. Martin Kravitz, the lead attorney for the hotel, on Monday described him as "bizarre" and said "he dressed slovenly to the deposition."

"His answers were vague, not very thoughtful," during the deposition, Kravitz said. "He wasn't angry ... This is not a guy who would have really stood out in your mind."

He added that Paddock was wearing "crappy flip-flops."

"You wonder what a guy like this is doing at the Cosmo," he said.

Aldean, who was named the Academy of Country Music's Entertainer of the Year in April 2017, was performing on the final night of the three-day Route 91 Harvest festival at the Las Vegas Village when the shots started. He later said via Instagram that he and his band were safe.

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"I still don't know what to say but wanted to let everyone know that Me and my Crew are safe. My Thoughts and prayers go out to everyone involved tonight," he wrote.

Vice President Mike Pence tweeted his condolences after the "senseless violence."

"The hearts and prayers of the American people are with you. You have our condolences and sympathies," he wrote.

"To the courageous first responders, thank you for your acts of bravery," he added.

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Hillary Clinton also expressed her grief in a tweet: "The crowd fled at the sound of gunshots. Imagine the deaths if the shooter had a silencer, which the NRA wants to make easier to get."

She added: "Our grief isn't enough. We can and must put politics aside, stand up to the NRA, and work together to try to stop this from happening again."

Police urged families looking to locate missing loved ones to call 1-866-535-5654.

Richie Duchon and Andrew Blankstein reported from Los Angeles. F. Brinley Bruton, Rachel Elbaum and Yuliya Talmazan reported from London. Pete Williams reported from Washington. Elizabeth Chuck and Tracy Connor reported from New York.