“I was just in my room doing my work when I heard a guy screaming, ‘Help, police—I’ve been robbed,’” Hostetter said. “I called HUPD from my cellphone. Two minutes later, there was like three police cars on the street.”

One of the suspects is described as a 40-year-old clean-shaven, black male. The suspect—standing at about 5’7’’ to 5’10’’ and weighing about 140 to 170 pounds—was wearing a tan winter jacket, according to a HUPD community advisory sent out yesterday. Lord was unable to give HUPD a detailed composite of the second suspect.

“The [suspect] was in the shadows, kind of behind him,” Catalano said. “It was hard for him to get a good look.”

“Facial features blur like nothing else in that situation,” Lord said. “You’re focusing on that gun and how you’re going to keep it from discharging.”

He chased the robbers moments after they fled and was almost run over trying to read their license plate number.

A nearby city resident who heard his screams ran out, according to Lord, and took him along in his car to follow the robbers—but to no avail.

Pennypacker residents said yesterday the robbey had made them anxious about security issues in the Union dorms.

“I find it ridiculous that you never see anyone around here—no security guard, no policeman. Not even during Head of the Charles,” said Joanna R. Miller ’08, a resident of Pennypacker.

Because the robbery did not occur on Harvard property, the Cambridge Police Department (CPD) is investigating the matter.

“Everytime there is an armed robbery, we put additional officers in the area,” said CPD spokeman Frank T. Pasquarello.

After the incident, HUPD reiterated that students should take precautions when walking after dark.

“Whenever possible, walk with someone else,” Catalano said. “One of the important things people can do is not to walk alone.”

—Staff writer Robin M. Peguero can be reached at peguero@fas.harvard.edu.