CHAPEL HILL, N.C. (AP) — Police were searching for both the weapon and the motive in a shooting at the University of North Carolina at Chapel Hill that left one faculty member dead and prompted an hours-long lockdown amid a search for the suspect.

The assailant in Monday afternoon’s shooting at a science building in the heart of the flagship university’s campus was taken into custody about an hour and a half after the gunfire was first reported, officials said at a news conference. Neither the suspect nor the victim were immediately identified and it wasn’t clear whether they knew each other. Formal charges were pending.

“To actually have the suspect in custody gives us an opportunity to figure out the why and even the how, and also helps us to uncover a motive and really just why this happened today. Why today, why at all?” UNC Police Chief Brian James said. “And we want to learn from this incident and we will certainly work to do our best to ensure that this never happens again on the UNC campus.”

UNC Police received a 911 call reporting shots fired at Caudill Labs just after 1 p.m. Monday, James said at a news conference. An emergency alert was issued and sirens sounded just two minutes later, issuing a lockdown warning that left worried students and staff barricading themselves inside dorms, bathrooms, classrooms and gyms.

Officers arriving at the lab building found a faculty member who had been fatally shot, James said. Based on “witness information,” police took the suspect into custody just after 2:30 p.m., according to the chief.

Jones declined to elaborate on the apprehension, but TV station WRAL reported it took place in a residential neighborhood near the campus.

The lockdown was lifted around 4:15 p.m.

No other injuries were reported.

“This loss is devastating, and the shooting damages the trust and safety that we so often take for granted in our campus community,” Chancellor Kevin Guskiewicz said.

Clayton Ulm, 23, a graduate student, said he was in a class of about 50 to 70 people when they were told to go into lockdown. The alarm system had gone off, but screens in the classroom had also glared with the lockdown order.

“Then there was quite a bit of panic as students were trying to figure out what to do,” Ulm said in a LinkedIn message while still in the classroom, heading into his third hour of lockdown. “Then we all started hiding beneath our chairs and under desks. Some students went and locked the doors.”

Students started listening to police scanners to try to get information about where the shooter was, Ulm said. The panic eventually subsided. And people were allowed to use the nearby restrooms. Still, he called it “surreal seeing the mass panic.”

About two hours after the first alert went out, officers were still arriving in droves, with about 50 police vehicles at the scene and helicopters circling over the school.

It took about an hour and a half to lift the lockdown after the arrest because authorities were making sure they had the right suspect in custody, James said.

Police also had received calls around campus about other potential victims and gunshots that needed to be checked out, he said.

“We had to ensure that the entire campus was safe,” James said.

James said it was unclear if the suspect knew the victim. He also said the weapon has not been found.

“We are looking for a firearm. It is too early to determine if the firearm was legally obtained,” he said.

Classes started at UNC, the nation’s first public university, a week ago. The university, with about 20,000 undergraduate students and 12,000 graduate students, canceled Tuesday classes.

Rushil Umaretiya, a freshman from northern Virginia, held a candle outside Caudill Laboratories Monday evening with two friends at his side. The computer science student had moved to Chapel Hill just two weeks ago and said he did not know the person who died. Umaretiya said he wanted to end a day of fear and uncertainty with a quiet moment of reflection in honor of the deceased faculty member.

“In my family, whenever someone passes, we light a candle, so I thought I’d come out and pay some respect to the community I’m trying to join,” he said. “It’s a scary time for a lot of people, like I have a lot of history with loss, so I think it’s just fear and a lot of mixed emotions.”

Ulm, the graduate student, said he had moved from Oklahoma to North Carolina for grad school just a couple months ago.

His mother called during the lockdown and was “crying profusely.”

She told him: “I knew I should’ve texted you yesterday, I was so worried... this was my greatest fear.”

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Robertson reported from Raleigh, North Carolina, and Rankin reported from Richmond, Virginia. Associated Press writers Sarah Brumfield in Silver Spring, Maryland, and Ben Finley in Norfolk, Virginia, contributed to this report.