Minghui Yu, a student in the Graduate School of Arts and Sciences, was hit by a car after fleeing an alleged assault Friday night, and subsequently died at St. Luke's Hospital. Police have since arrested a 14-year-old male in connection with the case, and the suspect has been charged with manslaughter in the second degree.

Yu was taken from the scene in critical condition to St. Luke's Hospital, where he died, surrounded by friends and faculty, from severe head trauma around 11:30 p.m.

"I heard a thud. I came to the gate, looked across the street, saw a commotion ... I saw the guy laying there." John Stathus, who witnessed the incident, said at the scene Friday night.

The suspect police arrested Saturday night for the robbery will be prosecuted for second-degree manslaughter as a juvenile offender, Associate Vice President for Public Safety James McShane said. Police will not release his name due to his status as a juvenile. NYPD had initially said Yu was fleeing from a robbery by several people, but has since labeled it an error and called it an assault.

Police have questioned two other minors who were present Friday night with the arrested suspect, but they were not charged. "It has been determined that those two kids were not involved. Only the one guy was involved," a police officer of NYPD's public information office said. The driver of the vehicle stopped immediately after hitting Yu, and police said no criminality is suspected.

As the suspect was being held inside the 26th Precinct, a throng of photographers gathered outside awaiting his transfer. His mother also waited outside, telling photographers to leave him alone and that Yu's death was not his intention. "He's only 14! He's only 14!" she shouted.

The University's Department of Public Safety released a security alert early Saturday morning with a surveillance photo that showed "two males who may have valuable information about this incident." The flier provided NYPD phone numbers for tips, but police said they could not confirm the accuracy of the photo.

"We had nothing to do with that photo. I don't know where it came from, and we are not saying that those are the guys that were involved in the incident," a detective of NYPD's public information office said. "I know for a fact that we are saying that that is not the people we are looking for."

Members of the Department of Public Safety did not return numerous requests for comment.

Yu had had dinner with his girlfriend, Chao Sun, on W. 125th Street Friday night, Junhua Shen, GSAS '09 and Yu's friend, said. After walking Sun to her home on W. 122nd and LaSalle streets, he began to walk back to his own apartment at 503 W. 121st Street when he was assaulted, Shen said.

Yu was a Ph.D. candidate in statistics at GSAS and a statistics teaching fellow. A native of China and a graduate of the University of Science and Technology of China, Yu was director of public relations for the Columbia University Chinese Students and Scholars Association.

"As a community we mourn the loss of one of our members, and especially of a young person with much to look forward to in a life of promise," University President Lee Bollinger said in a University-wide e-mail.

"Students become such an easy target," said Hui-Rung Huang, a GSAS student who lives in Yu's building. "It turns out students are actually extremely easy targets, extremely vulnerable."