The city of Watertown, Mass., has been effectively shut down as a manhunt is underway for the second suspect in the Boston Marathon bombing.

Residents were awakened overnight by heavy police presence and a dramatic shootout in Watertown that ended with the death of one of the Boston marathon bombing suspects while the second is still on the loose.

Officials say the suspects had hijacked a car in Cambridge, Mass., and drove to Watertown while being pursued by police.

Authorities used a news conference, robo-calls and Twitter to tell residents to shelter in place.

"Residents of Watertown asked to stay indoors," the Boston Police Department tweeted. "Do not answer door unless instructed by a police officer."

MORE: 1 Boston Bombing Marathon Suspect Dead, 1 'Armed and Dangerous,' Police Say

Public transportation has been suspended and authorities told people at closed stops and stations to go home. No vehicle traffic is allowed in Watertown. A no-fly zone is in place over the city.

"We are asking you to stay home, stay indoors," police said at a news conference this morning. "We are asking businesses not to open. We are asking people not to congregate outside. We're asking people not to go to mass transit."