At least 50 people have been killed and another 200 have been wounded in a mass shooting at a Las Vegas concert.
A gunman, named as 64-year-old local resident Stephen Paddock, opened fire from the 32nd floor of the Mandalay Bay Hotel towards an open-air music festival.
He was shot dead by officers in the hotel where a number of guns were found.
The attack is the worst mass shooting in recent US history.
US President Donald Trump tweeted his “warmest condolences and sympathies” to the victims and their families, and called the shooting “terrible”.
Sheriff Joe Lombardo described the shooting as a “lone wolf” attack. He said there was no information about Paddock’s motives.
“We have no idea what his belief system was,” he said.
He added that police were now confident they had located a woman, earlier named as Marilou Danley, who was thought to have been travelling with the gunman before the attack.
Sheriff Lombardo said he was unable to give accurate details of dead and wounded, but confirmed two off-duty police officers were among those killed.
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‘Attack will stun America’
By the BBC’s James Cook, in Las Vegas
This has been a mass shooting which has shocked Las Vegas – it has stunned this city. It is very clear that it will be an event which will stun the USA too, a country in which, regrettably, such mass shootings – even if on a lesser scale – are not uncommon.
As to to why the gunman may have carried out this attack, there is no indication of motive at this stage. He was said to have had a large arsenal, a huge number of weapons in that hotel room, which police finally stormed using explosives.
As to why he would have set himself up up there in that way, to do as he did, it is just so, so difficult to fathom.
Witnesses reported that hundreds of shots were fired.
Hundreds of people fled the scene and the sound of what appeared to be prolonged automatic gunfire could be heard on videos posted on social media.
Many hotels on the Las Vegas strip close to the scene remained on police lockdown and parts of Las Vegas Boulevard were shut.
People sheltered in hotels, restaurants and at Las Vegas McCarran airport.
A witness, Mike Thompson from London, told the BBC that he saw people running in total panic.
“One man had blood all over him and that’s when I knew something was seriously wrong.
“People were running and there was chaos.”
Concert-goer Mike McGarry told Reuters he lay on top of his children when the shots rang out.
“They’re 20, I’m 53. I lived a good life,” he said.
Some flights were diverted after news of the incident emerged.
The country music festival had been taking place since Friday at several hotels on the Las Vegas strip.
Singer Jason Aldean, who was rushed off stage when the shooting started, shared on Instagram that he was safe but heartbroken and did not know what to say.
“Tonight has been beyond horrific,” he wrote.
“It hurts my heart that this would happen to anyone who was just coming out to enjoy what should have been a fun night.”
Nevada has some of the least stringent gun laws in the United States.
People are allowed to carry weapons and do not have to register themselves as a gun-owner.
Background checks are done when people buy guns, but they are also allowed to sell them privately.
The state does not ban assault weapons, which include automatic or semi-automatic firearms.