A lone shooter opened fire on the main campus of the University of Nevada, Las Vegas, on Wednesday, killing three people and wounding a fourth before the suspect was shot dead by police, authorities said at a news briefing hours afterward.

Police declined to publicly identify the assailant, going so far as to avoid any mention of the suspect's gender, nor did they give any information about the four victims struck by gunfire - three fatally - or their connection to the university.

The surviving gunshot victim was listed in stable condition, according to Sheriff Kevin McMahill of the Las Vegas Metropolitan Police Department.

He said several other people suffered panic attacks during the pandemonium, and a number of officers were treated for minor injuries sustained during a search of the sprawling campus for any additional victims or suspects. None were found.

No mention was made of a possible motive for the violence, and police did not disclose the type of firearm used.

Vincent Perez, a professor at the school, known by its initials UNLV, told MSNBC by phone that he had heard a lot of 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 realized this is a real shooting, and there's an active shooter on campus."

Official details of the incident remained sketchy.

After receiving a call reporting gunfire on campus at about 11:45 a.m. (1945 GMT), law enforcement "immediately engaged the suspect in a shootout," UNLV police chief Adam Garcia told reporters. He said the suspect was fatally shot by campus police.

"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," the sheriff added.

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 "neutralized."

Police said the university would remain closed at least through Friday.

The UNLV campus, located less than 2 miles east of the Las Vegas Strip, has a student enrollment of some 25,000 undergraduates and 8,000 post-graduates and doctoral candidates.

The sheriff said many students he encountered appeared to have been badly shaken, recalling how people were likewise traumatized in the aftermath of a mass shooting in 2017, when a gunman opened fire from a high-rise hotel window onto a music festival below along the Las Vegas Strip. Sixty people were killed and hundreds more were wounded in what still ranks as the deadliest mass shooting by a single gunman in U.S. history.