A gunman opened fire on Monday night on the main campus of Michigan State University, killing three people and injuring five, before an hours-long manhunt for the suspect ended with his death, apparently from a self-inflicted gunshot, police said.

The 43-year-old gunman had no known affiliation to the university, and his motive remained a mystery, police said at an early morning news briefing more than five hours after the violence began on the sprawling East Lansing campus, about 90 miles northwest of Detroit.

Details about the sequence events remained sketchy, but Chris Rozman, interim deputy chief of the university police, said shots were fired in two locations – an academic building called Berkey Hall and the Michigan State University (MSU) Union building.

Police swarming the campus in response to the shooting, which began shortly after 8 pm, found victims at both locations, Rozman told reporters at the televised briefing.

Rozman said investigators had no information about the motive, adding that the university was not aware of any threats made to the campus before Monday’s bloodshed.

Rozman said three victims were killed and five were taken to a hospital in the nearby city of Lansing, the state capital, all of them listed in critical condition. Two of the dead were at Berkey Hall and the other at the MSU Union.

Officials declined to provide any details about the victims, some of whose identities and relationship to the university were still being determined, Rozman said.

The name and other information about the suspect were not immediately released, and police said they remained baffled by what precipitated the shooting.

“We have no idea why he came to campus to do this tonight,” Rozman told reporters.

The gunman was confirmed dead, from an apparently self-inflicted gunshot roughly four hours after the bloodshed had started, Rozman said.

“There is no longer a threat to campus. We believe there to be only one suspect in this incident,” he said.

Rozman also said the suspect “was contacted by law enforcement off campus” at one point, adding, “that scene is being investigated as a crime scene.”

It remained unclear whether the gunman was found dead after he was confronted by police, or whether he may have taken his own life during such a encounter.

About an hour earlier, MSU police had released two still images of the suspect from surveillance video that showed him walking into a building, then mounting a short flight of stairs, wearing a jacket, a baseball cap and a black mask over his lower face. He was holding what appeared to be a pistol in one hand.

Students, faculty and residents in surrounding off-campus neighborhoods of East Lansing had been told by authorities to “shelter in place” during the manhunt. That advisory was lifted once the suspect’s death was confirmed.