EAST LANSING, Mich. >> A gunman who opened fire at Michigan State University killed three people and wounded five, setting off an hours-long manhunt as frightened students hid in classrooms and cars. The shooter eventually killed himself, police announced early Tuesday.

Officials do not know why the 43-year-old man, whose name was not immediately released, targeted the campus. He was not a student or employee and had no affiliation with the university, according to campus police.

The shooting began Monday night at an academic building and later moved to the nearby student union, a popular gathering spot for students to eat or study. As hundreds of officers scoured the East Lansing campus, about 90 miles northwest of Detroit, students hid where they could. Four hours after the first shots were reported, police announced the man’s death.

“This truly has been a nightmare we’re living tonight,” said Chris Rozman, interim deputy chief of the campus police department.

Ryan Kunkel, 22, was attending a class in the Engineering Building when he became aware of the shooting from a university email. Kunkel and about 13 other students turned off the lights and acted like there “was a shooter right outside the door,” he said.

“Nothing came out of anyone’s mouth” for over four hours, he said.

“I wasn’t ready to accept that this is really going on next door,” Kunkel said. “This is supposed to be a place where I’m coming, learning and bettering myself. And instead, students are getting hurt.”

The shooting at Michigan State is the latest in what has become a deadly new year in the U.S. Dozens of people have died in mass shootings so far in 2023, most notably in California where 11 people were killed as they welcomed the Lunar New Year at a dance hall popular with older Asian Americans.

In 2022, there were more than 600 mass shootings in the U.S. in which at least four people were killed or wounded, according to the Gun Violence Archive.

“This is a uniquely American problem,” Michigan Gov. Gretchen Whitmer lamented.

Rozman, of the campus police, said two people were killed at Berkey Hall and another was killed at the MSU Union, while five people were in critical condition at Sparrow Hospital.

Police eventually confronted the shooter, who then died by a “self-inflicted gunshot wound,” Rozman said.

“We have no idea why he came to campus to do this tonight. That is part of our ongoing investigation,” the deputy chief said.

Ted Zimbo said he was walking to his residence hall when he encountered a woman with a “ton of blood on her.”

“She told me, ‘Someone came in our classroom and started shooting,’” Zimbo told The Associated Press. “Her hands were completely covered in blood. It was on her pants and her shoes. She said, ‘It’s my friend’s blood.’”

Zimbo said the woman left to find a friend’s car while he returned to his SUV and threw a blanket over himself to hide for three hours.

During the manhunt, WDIV-TV meteorologist Kim Adams, whose daughter attends Michigan State, told viewers that students were worn down by the hourslong saga.

“They’ve been hiding, all the lights off in a dark room,” Adams said.

Aedan Kelley, a junior who lives a half-mile east of campus, said he locked his doors and covered his windows “just in case.” Sirens were constant, and a helicopter hovered overhead.

“It’s all very frightening,” Kelley said. “And then I have all these people texting me wondering if I’m OK, which is overwhelming.”

Michigan State has about 50,000 students, including 19,000 who live on campus. All classes, sports and other activities were canceled for 48 hours.

Interim university President Teresa Woodruff said it would be a time “to think and grieve and come together.”

“This Spartan community — this family — will come back together,” Woodruff said.