Las Vegas Metropolitan Police spokesperson Todd Fasulo said that authorities recovered 42 firearms belonging to Stephen Paddock, the alleged gunman who killed 59 and injured more than 500 at a country music festival.
During a press conference, Clark County Sheriff Joseph Lombardo said that at least 50 people had been killed and more 400 were injured, but added that the precise number of victims could not be given.
A former accountant and a licensed private pilot, police said Paddock had had no known brushes with the law.
White House spokeswoman Sarah Huckabee Sanders said President Donald Trump was "briefed on the horrific tragedy in Las Vegas".
The Las Vegas company's stock dropped 5.58% to $30.77 a share, with its market valuation dropping to about $17.7 billion from almost $18.9 billion on Friday.
Two officials familiar with the investigation into the massacre, say authorities found at least 23 guns in the hotel room of the Las Vegas shooter.
People flee the Route 91 Harvest country music festival grounds after a active shooter was reported in Las Vegas, Nevada, on October 1, 2017.
There is still a lot they don't know about what motivated Paddock, described by officials as a "lone wolf", to launch the most deadly mass shooting in modern US history. "Some were falling, some were screaming and yelling and running".
Paddock shot from a hotel room on the 32nd floor of the Mandalay Bay Resort and Casino, located across the street from the outdoor concert.
Greg Abbott, governor of Texas, also said Monday that the news of violence in Las Vegas overnight is heartbreaking.
Lombardo identified the gunman as Stephen Paddock, 64, of Mesquite - a town outside of Las Vegas.
Islamic State has claimed to be behind the attack, but there is no evidence to support this possibility. He shot himself before police could break into his room.
Kodiak Yazzie, 36, said he and his girlfriend were watching Jason Aldean's performance when he heard what sounded like fireworks.
Mr Cipriani, who says his Robin Hood nickname is down to his habit of donating winnings to poor people, previous hit headlines after it was revealed he is banned from every single casino.
"My thoughts and prayers go out to everyone involved tonight", Aldean wrote on Instagram.
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