One Boston Marathon bomber dies after killing cop

One of the suspects in the Boston Marathon bombings was killed early Friday morning while fleeing after a shootout that left a Massachusetts Institute of Technology (MIT) campus police officer dead.

The dragnet is out for the second suspect, said to be the dead man's brother, who managed to get away after the shooting. Large parts of the area have been shut down, while Massachusetts governor Deval Patrick said residents of Boston and its neighbouring communities should ''stay indoors, with their doors locked''.

The surviving suspect was identified as Dzhokhar A. Tsarnaev, 19, of Cambridge, Massachusetts, a law enforcement official said. The one who was killed was identified as Tamerlan Tsarnaev, 26.

The authorities were investigating whether the dead man had a home-made bomb strapped to his body when he was killed, law enforcement officials said.

Three people died and more than 170 were hurt when two bombs exploded near the finish line of Monday's Boston Marathon.

Two men, later identified as the Boston marathon bomb suspects, hijacked a car at gunpoint.l

At 1 am local time Police chased the car as it headed to the Watertown area. A subsequent shootout left one of the two fatally injured.

Earlier the Federal Bureau of Investigation released several images of the two men they were hunting in relation to the bombing, one wearing a white cap, the other a black cap. The manhunt sent the Boston region into the grip of a security emergency, as hundreds of police officers conducted a wide search and all public transit services were suspended.

Col Timothy P Alben of the Massachusetts State Police said investigators believed that the two men were responsible for the death of the MIT police officer and the shooting of an officer with the Massachusetts Bay Transportation Authority, the region's transit authority. ''We believe these are the same individuals that were responsible for the bombing on Monday at the Boston Marathon,'' he said.

Officials said that the two men were of Chechen origin. Chechnya, a long-disputed, predominantly Muslim territory in southern Russia sought independence after the collapse of the Soviet Union and then fought two bloody wars with the Russian government.

Russian assaults on Chechnya were brutal and killed tens of thousands of civilians, as terrorist groups from the region staged attacks in central Russia.

In recent years, separatist militant groups have gone underground, and surviving leaders have embraced fundamentalist Islam.

The brothers have substantial presences on social media. On Vkontakte, Russia's most popular social media platform, the younger brother, Dzhokhar, describes his worldview as ''Islam'' and, asked to identify ''the main thing in life'', answers ''career and money''. He lists a series of affinity groups relating to Chechnya, and lists a verse from the Koran, ''Do good, because Allah loves those who do good.''

One former schoolmate of Dzhokhar Tsarnaev at Cambridge Rindge and Latin School in Massachusetts described him as ''very sweet,'' adding, ''I never heard anyone say a bad word about him.'' Another, Meron Woldemariam, 17, the manager of the school volleyball team said Tsarnaev had played for the team but left it in the middle of the season to wrestle. She described him as normal - sociable, friendly and fun to talk to. He was a senior when she was a freshman.

The older brother left a record on YouTube of his favorite clips, which included Russian rap videos, as well as testimonial from a young ethnic Russian man titled ''How I accepted Islam and became a Shiite,'' and a clip ''Seven Steps to Successful Prayer''.

Alvi Karimov, the spokesman for Ramzan A Kadyrov, leader of Chechnya, seemed to distance Chechnya from the attack. He said the Tsarnaev brothers had not lived in Chechnya for many years. He told the Interfax news service that, according to preliminary information, the family ''moved to a different region of the Russian Federation from Chechnya many years ago.''

He continued, ''Then the family lived for a long time in Kazakhstan, and from there moved to the United States, where the members of the family received residency permits.''