CHAPEL HILL, N.C. - A University of North Carolina graduate student walked into a classroom building, shot his faculty adviser and quickly left, authorities said a day after the attack paralyzed the campus as police searched for the gunman.

Tailei Qi, 34, was charged Tuesday with first degree murder and having a gun on educational property in Monday’s killing of Zijie Yan inside a science building at the state’s flagship public university.

Chapel Hill Police arrested Mr. Qi without force in a residential neighborhood near campus within two hours of the attack, UNC Police Chief Brian James said at a news conference.

Investigators were trying to determine a motive and searching for the gun, Chief James said. He declined to specify where in Caudill Labs Yan was killed, saying officers are still looking at evidence. Mr. Qi was already gone when a team of officers reached the building, Chief James said.

Mr. Yan was “a beloved colleague, mentor and a friend of so many on our campus and a father to two young children,” UNC Chancellor Kevin Guskiewicz at the news conference.

On Wednesday afternoon, the school’s iconic Bell Tower will ring in honor of Mr. Yan’s memory and students are encouraged to take a moment of silence, he said. The school also canceled classes until Thursday.

Earlier Tuesday, Mr. Qi briefly appeared in Orange County Superior Court in Hillsborough. Judge Sherri Murrell ordered Mr. Qi to remain jailed without bond and scheduled his next court date for Sept. 18.

After the hearing, Mr. Qi bowed to the judge, his Mandarin interpreter, public defender Dana Graves and the guards who took him away in handcuffs.

Ms. Graves left court without talking to reporters and did not immediately respond to an email seeking comment.

Mr. Yan was an associate professor in the Department of Applied Physical Sciences who had worked for the university since July 2019, Chancellor Guskiewicz said Tuesday. He led the Yan Research Group, which Mr. Qi joined last year, according to the group’s UNC webpage.

Mr. Yan was a respected and approachable professor and research adviser who was deeply knowledgeable about the field, said Wen Liu, a 2022 graduate who worked in the lab for three years.

He was somewhat reserved, yet always willing to answer questions with patience and respect and advise lab members who got stuck in their research, Mr. Liu said.

“For hours he would just be doing things and explaining along the way,” said Mr. Liu, who was a “newbie undergrad in the field” at the time and also worked with Mr. Qi in the lab. Mr. Qi seemed passionate about research, curious about others’ work and “pretty sociable,” Mr. Liu said.

The lab’s main goals were making and studying nanoparticles under the effect of light, using lasers, he said. The work has potential applications in medicine and other fields.