A "lone wolf" shooter opened fire on a country music festival in Las Vegas on Sunday night, killing at least 50 and injuring over 400 people.
It was the deadliest mass shooting in modern US history, surpassing the 49 deaths at Pulse nightclub in Orlando in June 2016.
The sole suspect, who fired at attendees of the Route 91 Harvest Festival from a room at the Mandalay Bay hotel and casino that overlooked the event, is believed to have committed suicide, police said.
The suspect has been named as 64-year-old Las Vegas native Stephen Paddock. His motives are unknown and he has no known links to any terror groups.
Las Vegas police released a photo of the dead suspect's "companion," Marilou Danley, announcing that she was wanted for questioning, before later indicating they had reached her and suggesting they did not believe she was involved.
Video posted online shows the country singer Jason Aldean's performance being interrupted by the sound of automatic gunfire, with audience members screaming "get down" and "stay down," reports the New York Times.
Sheriff Joseph Lombardo of Clark County told reporters during a press conference that several SWAT teams were sent to the Mandalay Bay after emergency calls were made at 10:08 PM.
Of the operation to find and stop the gunman, Lombardo said, "Through investigation and response, we determined there was a shooter on the 32nd floor of the Mandalay Bay. Officers responded to that location and engaged the suspect at that location. He is dead... Right now, we believe it is a sole actor—a lone wolf-type actor—and we have the place under control."
When asked about the casualties, Lombardo confirmed that two of the dead were off-duty police officers.
"I have two police officers who are currently at the hospital, one in critical condition and the other with minor injuries," he said. "There were other police officers that were off duty attending the concert, that have expired. We don't have those individuals identified at this point."
In a later press conference, Lombardo said officers found "numerous firearms" in Paddock's room, and that the investigation ahead is going to be "long and tedious."
President Trump was briefed about the shooting, according to the White House.
World leaders, including British prime minister Theresa May and Swedish PM Stefan Löfven, have joined artists who were performing at the Route 91 festival in tweeting prayers and messages of condolence.
This post has been updated to reflect the latest police statement on the shooter's death after earlier reports suggested he was killed by police, and to include updated estimates of the number of people injured in the attack.