The police killed one of the suspected Boston marathon bombing suspects in a shootout early Friday and pursued a chaotic deadly street-to-street manhunt for his accomplice, officials said.

The two men, dubbed “suspect one” and “suspect two” by the FBI, led police special forces on a violent cavalcade that left inhabitants of towns around Boston cowering in their homes as gunfire and explosions erupted through the night.

One police officer was killed and another wounded in the operation, Boston police commissioner Ed Davis said. Davis also confirmed that suspect one had been killed.

The man, whose identity is still not known, was shot several times and declared dead in hospital. The Police told inhabitants of Watertown to stay indoors and away from windows as they hunted the second man believed to have planted the bombs that killed three people and injured about 180 at the Boston marathon on Monday.

The surviving fugitive was “armed and dangerous,” Davis said. “We believe this to be a terrorist, we believe this to be a man who has come here to kill people,” the police chief told reporters. The suspects first tried to rob a convenience story in Cambridge, across the river from Boston, Davis said. They then went to the Massachusetts Institute of Technology where one campus police officer was shot several times and died, the commissioner added. The pair then hijacked a Mercedes car and eventually let the driver out in Watertown, which is close to MIT, Davis added.

The chase went on through Watertown where explosions and gunfire were heard in several districts. During a shooutout, one wanted man was hit and died later in hospital, Davis said. Another police officer was also wounded. The second suspect, who has been shown in pictures wearing a white baseball cap, escaped.

MIT students were kept in a lockdown for three hours after the shooting on campus. The police with rifles flooded the streets, and search helicopters patrolled the skies. MIT, one of the world’s top universities, is in Cambridge, just across the Charles River from Boston where the double bomb attack was staged on Monday in the worst militant attack on the United States since the September 11 atrocities in 2001.

Hours before the manhunt, the FBI released pictures and video of the two suspects, appealing for help to identify the pair who were carrying large backpacks. Both appeared to be young men, one dressed in a white baseball cap and the other in a black cap. The FBI gave no details of their identities or origin, naming them only as suspect one and suspect two. Two bombs were placed around the marathon finish line on Monday, spraying nails, ball bearings and other metal fragments into massed spectators, many of whom suffered horrific injuries. The men are seen in the video walking calmly, one a few paces behind the other, weaving between crowds on Boston’s Boylston Street where the race finished.

President Barack Obama vowed to the people of Boston Thursday that the “evil” bombers would be brought to justice. At a special service at Boston’s Cathedral of the Holy Cross, Obama vowed: “Yes, we will find you, and yes, you will face justice.”

“We will find you, we will hold you accountable,” he told a congregation of 2,000, including relatives of the dead, survivors of the blasts, rescuers and city leaders.

“If they sought to intimidate us, to terrorize us,” Obama said, then “it should be pretty clear by now that they picked the wrong city to do it.” Boston has held emotional tributes to the dead — eight-year-old Martin Richard, Boston University graduate student Lu Lingzi of China and Krystle Campbell, a restaurant manager. Obama paid tribute to all three at the service. More than 100 of the wounded have left Boston hospitals and fewer than 10 of those still in hospital remain in critical condition. Some will require new operations, doctors said.