A gunman killed at least 50 people and wounded more than 400 at a country music festival on the Las Vegas Strip on Sunday, raining down rapid fire from the 32nd floor of a hotel for several minutes before he was shot dead by police.
The death toll, which police emphasized was preliminary and tentative, would make the attack the deadliest mass shooting in United States history, eclipsing last year's massacre of 49 people at an Orlando night club.
Thousands of panicked people fled the scene, in some cases trampling one another as law enforcement officers scrambled to locate and kill the gunman. Shocked concertgoers, some with blood on their clothes, wandered the streets after the attack.
The suspect was a local Las Vegas man who acted alone and was not believed to be connected to any militant group, Clark County Sheriff Joseph Lombardo told reporters.
Police identified the gunman as area resident Stephen Paddock, 64, but said they had no information yet about his motive.
He was not believed to be connected to any militant group, Clark County Sheriff Joseph Lombardo told reporters.
"We have no idea what his belief system was," Lombardo said.
"Right now, we believe he was the sole aggressor and the scene is static."
"We've located numerous firearms within the room that he occupied," Lombardo said.
Authorities believed they had located Paddock's roommate, who they identified as Marilou Danley.
He gave no details of whether she was suspected of involvement in the attack but described her as an "associate".
Police had located two cars that belonged to the suspect.
The dead included one off-duty police officer, while at least one other officer was critically injured, Lombardo said. Police warned the death toll may rise.
He said rumors of other shootings or explosives such as car bombs in the area were false.
The gunfire came from the 32nd floor of the Mandalay Bay, where the gunman was killed, he said.
The shooting broke out on the last night of the three-day Route 91 Harvest festival, a sold-out event attended by thousands and featuring top acts such as Eric Church, Sam Hunt and Jason Aldean.
Mike McGarry, a 53-year-old financial adviser from Philadelphia, said he was at the concert when he heard hundreds of shots ring out.
"It was crazy - I laid on top of the kids. They're 20. I'm 53. I lived a good life," McGarry said. The back of his shirt bore footmarks, after people ran over him in the panicked crowd.
Many casinos in the area locked their doors during the incident to keep out any potential attackers, some using handcuffs to do so, according to witnesses.
"Caesar's Palace had locked their doors. They wouldn't let you in," said Adam Mitchell, a 31-year-old tourist visiting from Britain.
A witness named Christine told CNN both she and her husband had separately taken shooting victims to two hospitals, the University Medical Center and the Sunrise Hospital and Medical Center.
"The shots just kept coming," she said. "Everyone was telling us 'run, run as fast as you can'."
The concert venue was in an outdoor area known as Las Vegas Village, across the Strip from the Mandalay Bay and the Luxor hotels.
Las Vegas is a major resort city, known primarily for its gambling, shopping and nightlife, which would have been packed at time the shooting broke out shortly after 10pm. (5pm NZT).
United States media, including Fox News, reported that Aldean was performing around 10.45 p.m. local time on Sunday when the rampage began but that he had been bundled safely off stage at the event outside the Mandalay Bay Resort and Casino in the Nevada gambling mecca. CNN reported all the artists were safe.
Police have disclosed no information that would suggest a motive for the shooting.
Even so, the rampage was reminiscent of a mass shooting at a Paris rock concert in November 2015 that killed 89 people, part of a coordinated attack by Islamist militants that left 130 dead.
Earlier Las Vegas Metropolitan Police Department said on Twitter: "Confirming that one suspect is down. This is an active investigation. Again, please do not head down to the Strip at this time."
Just after 12.30am local time (8.30pm NZ time), police said on Twitter they believed the "downed" suspect was the only gunman.
The Mandalay Bay hotel is near McCarran International Airport, which said on Twitter it had temporarily halted flights after the shooting.
Later, the airport said that some flights had resumed
Getty Images has posted photos of bodies on the ground covered in blood and people being carried away from the Route 91 Harvest country music festival in Las Vegas.
Other photos show panicked people running from the scene and taking cover on the ground.
One Twitter user posted that the casino hotel was on lockdown, while another, citing police scanners, said two gunmen who had shot at a bodyguard and police were on the 32nd floor.
Video clips posted online showed what sounded like automatic weapons as panicked concertgoers fled, dropped to the ground screaming.
Witnesses heard numerous gunshots at the hotel, where police tactical teams were searching for the attacker, according to reports on CNN and in the New York Times.
An Australian tourist named Danny told CNN he was in the Mandalay Bay and described chaos at the scene as officers ran into the building's lifts.
"They were going up, they were coming down, they were going this way, that way. We were told to get out, told to get in - one shooter's up there still, we were told by police, and one's roaming around."
SWAT officers were everywhere, he said. "A lot of people heard gunshots - the initial gunshots were apparently machine gun fire."
Authorities could not be reached to confirm those details.
