Thousands of heavily armed police went door-to-door through a Massachusetts town on Friday in an unprecedented massive hunt for the remaining Boston marathon bombing fugitive.
Authorities halted all public bus and train services in the Boston region and told hundreds of thousands of people in several towns around Watertown to stay home in a bid to isolate the suspect.
Fleets of buses were sent to Watertown to ferry out nervous inhabitants. Those who stay were ordered to remain in their homes and only answer the door if they were sure it was a police officer.
More than 9,000 police, many armed with shotguns and automatic rifles, were sent to the town to find Suspect Two, one of two young men suspected of having carried out the bomb attack on Monday in which three people died and 180 were injured.
The hunt was concentrated on about 1.5 square miles (3.8 square kilometers) of Watertown, a quiet suburb of 35,000 people.
One police officer was killed and another wounded in shootouts in which the other suspect was fatally wounded in the early hours of Friday. The fugitives led police on a chaotic chase to Watertown.
Explosions and gunfire could be heard throughout the night as police chased the suspects.