A man on a double decker bus on the Las Vegas Strip pulled out a gun and opened fire, killing one person and wounding another before barricading himself inside in a stand-off that lasted hours.
The siege began at about 11am local time on Saturday as the bus stopped on Las Vegas Boulevard, near the Cosmopolitan hotel-casino.
"He was on the bus. He was shooting people on the bus. He was just contained to that location. He never exited the bus," Clark County assistant sheriff Tom Roberts said.
Two people were taken to the hospital after the shooting, University Medical Centre spokeswoman Danita Cohen said. One died and the other was said to be in a fair condition.
For hours, crisis negotiators, robots and armoured vehicles surrounded the bus with authorities uncertain if there were any more victims inside.
Meanwhile, officers swept into the casinos to warn tourists to bunker down until further notice, leaving the normally bustling pedestrian areas and a road notorious for taxi-to-taxi traffic empty.
The Strip was shut down in both directions.
Some in the Cosmopolitan - hotel guests out over their balconies and party people on the pool deck - saw the tense situation unfold below.
Former basketball player Scot Pollard, who is staying at the Cosmopolitan, said he was at a bar at the hotel-casino around 11am when he saw several people, including staff, running through the area towards the casino, screaming "Get out of the way".
"We can hear them negotiating. We can hear them saying things like, 'No one else needs to get hurt', 'Come out with your hands up. We are not going anywhere. We are not leaving', " he said.
Visitors were also hiding inside some of the other prominent casino properties affected, including the Bellagio, Paris, Planet Hollywood and Bally, which in addition to hotels and casinos also hold restaurants, shops and attractions.
Las Vegas police officer Larry Hadfield said the man, who had a handgun, gave himself up just before 3.30pm without incident.
Police did not open fire and said they believe the man is the only suspect.
They ruled out terrorism or any connection to an earlier robbery nearby that shut down a part of the Bellagio.
By 4pm, pedestrians were back in the area and northbound traffic on Las Vegas boulevard had reopened while investigators worked to clean up the other lane where the bus was still grounded.
The bus is operated by the Regional Transportation Commission of Southern Nevada. The agency said its bus driver was not hurt.
It is not known how many people were on the bus at the time of the shooting but it appears that those who were there were able to flee.
Police set up a hotline for passengers to report what they witnessed.