Authorities said surveillance tape recorded late Thursday showed the suspect known for the white hat during a robbery of a convenience store in Cambridge, near the campus of the Massachusetts Institute of Technology, where a university police officer was killed while responding to a report of a disturbance, said State Police Col Timothy Alben. The officer died of multiple gunshot wounds.
From there, authorities say, the two men carjacked a man in a Mercedes-Benz, keeping him with them in the car for half an hour before releasing him at a gas station in Cambridge. The man was not injured.
The search for the vehicle led to a chase that ended in Watertown, where authorities said the suspects threw explosive devices from the car and exchanged gunfire with police. A transit police officer was seriously injured during the chase, authorities said.