A Nassau Community College student who was robbed on campus Tuesday afternoon may have been targeted by someone who knew him, police said Wednesday.

The student seemed to know one of his assailants by "his street name," and the two are possibly acquaintances from the college or the Hempstead area, Nassau County police Insp. Kenneth Lack said Wednesday at a news conference.

Two men approached the 20-year-old man as he walked out of North Hall, heading east on Miller Avenue, around 4:15 p.m. in East Garden City, Lack said.

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One suspect hit the student in the head from behind with a black handgun, and stole a Rolex watch, cellphone and gold chain, Lack said. The men drove away in an older model gray Mustang, Lack said Wednesday at a news conference.

One suspect is his 20s, 5-foot-7-inches and weighing 150 pounds, police said. The second is 6-feet tall and 220 pounds.

Lack said it is possible the student, who suffered a contusion to his face, was targeted.

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Lack said the crime is the first robbery of the year on the campus, which he called "a very safe campus. "

"This type of crime in infrequent," he said.

In 2012, there were two pedestrian robberies, with one arrest, Lack said. There were five robberies in 2013, with three arrests, and none in 2014, Lack said.

In a statement, Joseph Muscarella, vice president for facilities management at the college, said NCC is "cooperating fully with the investigation."

"It is apparent that the victim knew one of the alleged assailants," Muscarella said.

He said "members of the campus community" are urged to report suspicious activity to the Department of Public Safety at 516-572-7100.

Lack said the university has 80 unarmed campus officers, half of whom work part time. Two Nassau officers also patrol the campus as part of their beat, Lack said.

Authorities ask anyone with information about the robbery to call 1-800-244-8477.