A 14-year-old boy is under arrest and another two boys were questioned yesterday in the death of a Columbia University graduate student who ran into the path of an oncoming car as he was being assaulted near the school.

The student, Minghui Yu, 24, had just escorted his girlfriend, Chao Sun, home to her apartment after the two had made dinner together, according to a friend of the couple. The walk back would have taken less than five minutes, but Yu didn’t make it halfway before he was attacked.

The teenagers were all under age 16, police said. They were waiting on Broadway and allegedly hassled Yu as he passed by late Saturday evening.

Police said one of the boys allegedly hit Yu as he began crossing the street while the others looked on. To escape, Yu ran back onto Broadway at 122nd Street and was struck by a sport utility vehicle in the southbound lane.

The driver stayed on scene and was not charged with a crime. The 14-year-old, who was not identified because of his age, has been charged with manslaughter. Police said it was unclear whether the other two would be charged.

Yu had been in the country for two years, and had met his girlfriend eight months ago. The two were very close, a friend of Ms. Sun said yesterday, and both of their names were posted next to the doorbell of her Broadway apartment two blocks north of his.

Ms. Sun spent most of yesterday with friends in Yu’s apartment on 121st Street waiting for news from police.

“She’s doing her best,” the friend, Yue Jiang, 24, said. “It’s a tough time.”

Mr. Jiang, who lives in Union City, said Ms. Sun had invited him to meet Yu a week ago.

“He’s very nice, very smart,” Mr. Jiang said. “I never thought it would be the first meeting, but also the last.”

Yu, an only child from Weifang City, a large city in Shandong Province, had attended the University of Science and Technology of China , a top-tier school, a representative of the Chinese consulate said. He came to New York in 2006 to begin doctoral studies in statistics.

The Chinese consul for the overseas affairs section, Yi Liu, said the consulate was working to help Yu’s parents, who were not identified, obtain visas to fly to New York.

“Hopefully they can come within one week,” Ms. Liu said, adding that funeral arrangements for Yu would be decided after they arrive.

Columbia University and the Chinese Students and Scholars Association announced that they would be holding memorial services in the coming week. Yu was the chairman of public relations for the association.

The death rattled some foreign students on campus, despite assurances from the university president, Lee Bollinger, “that the area of Morningside Heights is within one of the safest precincts in the city.”

Mi Yiang, 23, a Columbia graduate student who attended college with Ms. Sun in China, and who passed by her apartment building yesterday afternoon to pay his respects, said the incident had worried him.

“I think it’s not that safe as I imagined,” Mr. Yiang said, noting that he had received several notices about crimes around campus since arriving in New York six months ago.