Three people were killed and a fourth wounded by a lone attacker who opened fire on a university campus in Las Vegas, Nevada, on Wednesday.
The suspected gunman, who was not identified, was shot dead by campus officers during the incident at the University of Nevada Las Vegas, police said.
The wounded person was in stable condition, Sheriff Kevin McMahill of the Las Vegas Metropolitan Police Department said. No details were given about those who died.
Several other people suffered panic attacks during the chaos, said Mr McMahill.
Several officers were treated for minor injuries sustained during a search of the sprawling campus for any additional victims or suspects, but none were found, Reuters reported.
No motive for the violence or details of the weapon were given by police.
UNLV professor Vincent Perez told MSNBC by phone that he had heard gunfire before taking cover on campus.
“I would say just seven, eight shots, one after another, loud and very loud,” he said. “As soon as we heard that, we ran back inside and we realised this is a real shooting, and there's an active shooter on campus.”
After receiving a call reporting gunfire on campus at about 11.45am local time, police “immediately engaged the suspect in a shoot-out”, UNLV police chief Adam Garcia said.
“If it hadn't been for the heroic actions of one of those police officers who responded, there could have been countless additional lives taken,” Mr McMahill said.
The shooting began on fourth floor of Beam Hall, a building that houses the university's business school, then moved to other floors before finally ending outside where the suspect was “neutralised”, he said.
Police said the university would remain closed on Friday.
The UNLV campus, less than 3km east of the Las Vegas Strip, has 25,000 undergraduate students and 8,000 postgraduates and doctoral candidates.
Las Vegas is the site of America's deadliest mass shooting. In 2017, a gunman opened fire on people attending a music festival on the famous Las Vegas Strip, killing 60 and wounding more than 400.