Follow the latest updates on the mass shooting at Michigan State University.

On Monday night, the usually busy streets of Michigan State University’s sprawling 5,200-acre campus fell silent after a gunman opened fire in two buildings, killing three people and wounding five others.

For hours, students, faculty and staff sheltered in place, many in dormitories and in other campus buildings, as hundreds of police officers searched for the gunman.

Students across the campus in East Lansing, more than 80 miles northwest of Detroit, expressed fear. Among them was Jane Nodland, a senior nursing major, who on Monday night was at the university’s student union building to do homework with her boyfriend. She heard three gunshots and quickly dove into a corner before sprinting out of the building. “I thought I was going to die,” Ms. Nodland said. “It sounded like he was right there.”

Here’s what we know, and don’t know, about the shooting so far.

The gunman first opened fire at Berkey Hall, home to the school’s college of arts and sciences, and later at the Michigan State student union, according to the authorities. The two buildings, which are minutes from each other on Grand River Avenue, were both unlocked and open to the public.

At about 8:30 p.m. local time, the university sent an email alerting students, many of whom were in dormitories, libraries and other campus buildings, to secure in place or evacuate safely while the authorities searched for the shooter.

After a three-hour manhunt, the university police said the gunman was found off campus and had died from a self-inflicted gunshot wound. Shelter-in-place orders were lifted, and students quickly returned to their homes or were reunited with their families.

“This truly has been a nightmare that we are living tonight but we have remained laser focused on the safety of our students,” Chris Rozman, the interim deputy university police chief, said during a news conference. Teresa K. Woodruff, the interim president of Michigan State, said it was a day of “shock and heartbreak.”

The identities of the victims, and details about their connection to the university, have not yet been released. As of Tuesday morning, the five people who were wounded were all in critical condition and were being treated at Sparrow Hospital, the authorities said.

Very few details are known. The authorities have not yet identified the suspect but said he was a 43-year-old man who was not affiliated with the university. “We have no idea why he came to campus tonight,” Chief Rozman said.

As of Tuesday morning, the motive of the gunman was unclear. The authorities also had not announced what type of weapon or weapons were used in the shooting.

A news conference, where more details could be released, is scheduled for Tuesday morning. An investigation into the shooting could take weeks, according to an F.B.I. spokesman.

In the meantime, all campus activities, including classes and athletics, have been canceled for two days. The authorities have urged people to avoid coming to campus on Tuesday. East Lansing Public Schools will also be closed on Tuesday.