What to Know
At least 58 people were killed and hundreds more sent to hospitals
The gunman has been identified as Stephen Paddock, of Mesquite, Nevada
Paddock was found dead in his 32nd floor room in the Mandalay Bay hotel
Witnesses described relentless gunfire and victims falling before them after a man began shooting at a crowd of thousands at a concert on the Las Vegas Strip Sunday night, killing 58 people and injuring more than 500 in the deadliest mass shooting in modern American history.
The gunman opened fire around 10 p.m. from the 32nd floor of the Mandalay Bay Resort and Casino, taking aim at people listening to country singer Jason Aldean during the closing night of the three-day Route 91 Music Festival across Las Vegas Boulevard.
A musician at the concert, Carlos Sosa, said he looked to the sky when a woman next to him thought she heard fireworks. When he did not see any, he looked down and recalled seeing "mini-explosions" -- likely bullets or shrapnel -- on the ground.
"I didn't think it was real until I saw somebody lying on the ground with blood," Sosa said. "People were screaming and asking for belts and handkerchiefs. The shooting was still happening. We didn't know it was somebody from the hotel, we thought it was somebody on the ground."
Robert Anthony, who was in the parking lot of the Tropicana Las Vegas when the gunfire started, saw "a mob of people pouring out," looking distraught and confused.
"I heard loud, sustained gunfire," said Anthony, of Santa Monica, California. "It was terrifying. It was shocking. It stopped, it started again.”
Anthony said that the crowd headed into the MGM Grand Las Vegas and but pushed back out after reports of a shooter in the MGM.
"There was complete pandemonium," he said. "People were trying to cross back to the other side of the street again. No one knew where to go.
"I saw one person in the back of a pickup truck getting CPR. It was a very shocking scene, and it just seemed to go on forever," he said.
Authorities identified the shooter as Stephen Craig Paddock, 64, of Mesquite, Nevada, who they believe killed himself before police entered his room. He is thought to have checked into the room on Sept. 28 and had more than 10 rifles with him.
Law enforcement officers said that Paddock had been gambling significant amounts of money at Las Vegas casinos in past weeks, including more than $20,000 and $30,000 in a single day.
Concertgoers and others said that at first the crowd was confused by the noise. Amanda Mattoon said that initially she heard three pops, which she thought were from a cap gun or fireworks.
"And then they started clearing the stage," she said. "All the performers started running and everyone started dropping on the ground and shots just kept going and going and going."
Another concertgoer, Brianna Taylor, said it took a few moments for everyone to understand they were in danger. She also described pops, "almost like the little party poppers you use on New Year's," she said. But then Jason Aldean left the stage, the concert shut down and all of the lights came on, she said.
"I think when that went down we realized that we were in serious danger, so everyone got down," she said. "People were trying to decide whether or not if they needed to run."
Video posted to social media showed a chaotic scene as people scrambled for cover and tried to stay low to the ground, many screaming as they realized what was happening. Images from a few minutes after the shooting ended showed gruesome injuries, as people tried to help the injured, with cars and trucks of fleeing concertgoers being used to take wounded people directly to the hospital. A photo from a photographer from the Las Vegas Review-Journal photographer showed one injured person being moved in a wheelbarrow.
Mike Cronk, a retired teacher, describing loading four victims into a pick-up truck, then flagging down an ambulence. But as they transfered one young man, he died.
"He passed away there, in my arms as we were on the curbside," he told NBC News.
A witness, Meghan Kearney, told MSNBC that she heard what sounded like firecrackers
"Then all of a sudden we heard what sounded like a machine gun," she said. "People started screaming that they were hit. When we started running out, there were probably a couple hundred [people] on the ground.
"People kept dropping and dropping… People were getting shot one foot away from us," she said. "People were trying to save their friends. There were gunshots everywhere. Helping them would've meant that we got shot, too."
A performer, Jake Owen, said he was standing about 50 feet 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 passed victims covered in blood until he found shelter in his bus. The gunfire still had not stopped by the time he got there, he said.
"It wasn't something that was quick,” he said. "It was chaos for a pure seven to 10 minutes."
Another concertgoer, Ivetta Saldana, told the Las Vegas Review-Journal that she hid in a sewer.
"It was a horror show," she said. "People were standing around, then they hit the floor."
A couple, Matt and Robyn Webb, told the Las Vegas Review-Journal that they sheltered underneath their seats listening to burst after burst of gunfire.
"It just kept coming," Robyn Webb said. "It was relentless."
When they eventually evacuated, they said they saw as many as 20 people lying in the street bleeding.
"That's when we knew for sure it was real," Matt Webb said.
Another witness told CNN she heard round after round of gunfire.
"Everyone was running, you could see people getting shot," Gail Davis said. I’ve never been that scared in my life,” she added. “To have this happen, I can’t wrap my mind around it.”