"I wasn't going to wait around and be held hostage," said Cecily A. Flemings '03, one of the students who fled the lecture hall.

Mitten, Teaching Fellow Marc A. Lindemann and one student--Kris A. Garin '01--remained in the room with the man until police arrived.

The man demanded a cell phone to call the police, but when none of those present had one to offer, he said he would "wait until the police contact us," according to Lindemann.

Leong then walked back up to the center of the room, sat down and began drinking a student's soda that had been left behind in the rush, witnesses said. He mentioned that he had put up posters this week around campus but that everyone had ignored them. He did not specify the type of posters.

As the students fled the room, others in the Science Center followed them. One student set off the building's fire alarm, and the building was evacuated without incident.

Emergency units were on scene within minutes of the threat. By 10 a.m., Cambridge Police Department (CPD) officers sealed the streets around the Science Center with police line tape.

Cambridge Emergency Management also responded to the threat, joining two companies of the Cambridge Fire Department, including ladder trucks and heavy rescue units.