Two young men, armed with guns and explosives in what appeared to be backpacks, engaged in a violent standoff with dozens of police on a street in Watertown, Mass., Thursday night, a resident said.
Andrew Kitzenburg, 29, said he looked out of this third floor window to see two young men of slight build in jackets shooting at dozens of police officers from behind a black Mercedes SUV. The officers and the men were 70 yards apart, he said, and engaged in "constant gunfire."
A police SUV "drove towards the shooters," he said, and was shot at until it was severely damaged. It rolled out of control, Mr. Kitzenberg said, and crashed into two cars in his driveway.
The two shooters, he said, had a large and unwieldy bomb. "They lit it, still in the middle of the gunfire, and threw it. But it went 20 yards at most." It exploded, he said, and one of the two men ran towards the gathered police officers. He was tackled, but it was not clear if he was shot, Mr. Kitzenberg said.
The other, he said, got back into the SUV, turned it towards officers and "put the pedal to the metal." The car "went right through the cops, broke right through and continued west."
The two men left "a few backpacks right by the car, and there is a bomb robot out there now." Police had told residents to stay away from their windows, he said.
The standoff came within hours of an incident at the Massachusetts Institute of Technology in which a campus police officer was shot and killed.
The officer, who was not named, responded to a report of a disturbance near Vassar and Main Streets, the Middlesex County District Attorney Michael Pelgro said in a statement early Friday. He was found, the statement said with "multiple gunshot wounds" and taken to Massachusetts General Hospital where he was pronounced dead.
M.I.T. said in an update on its campus alert Web site after midnight that the "shooter remains at large, police continue to search the campus," and asked students to stay indoors until further notice.
At the campus, helicopters whirred overhead, and police cars were dotted through the streets. A crime scene was cordoned off, and at least one dog unit was on the scene.
The two incidents came as the area was already on edge following the bombings at the Boston Marathon on Monday.