Police are hunting in Watertown, 10-km from Boston, for someone they believe is the white-hatted "suspect number 2" in the Marathon bombings, after a police officer was shot dead last night on the Massachusetts Institute of Technology (MIT) campus.
The two Boston Marathon bombing suspects are believed to be brothers of Chechen-origin, media reports said as authorities here ordered lockdown of the city to hunt for the surviving suspect after the other one was killed in a shootout with police.
The suspect at large is 19-year-old Dzhokhar Tsarnaev and was born in Kyrgyzstan, NBC News said. He had a Massachusetts driver's license, it said.
The dead suspect was identified as 26-year-old Tamerlan Tsarnaev. He was born in Russia.
One suspect was killed in a shootout with police in Watertown, while the second fled on foot, State Police Colonel Timonty Alben said in an early morning press conference.
Police are "consistent with the description of suspect No 2 who was involved in Monday's bombing at the Boston Marathon," Alben said in a reference to the man in the white hat seen in images released by the FBI yesterday.
Earlier the FBI released pictures and videos of two suspects and sought the public's help in identifying the men who are seen carrying backpacks near the finish line of the race before the blasts that killed three persons and injured over 180.
"He is a white skinned Caucasian male with longer brown curly hair. You have the picture, you have seen it, that's the individual we are looking for...suspect number 1 has been shot dead," said another city police official.
Boston Police Commissioner Edward F Davis said that they "believe this to be a terrorist." "We believe this to be a man here to kill people."
Police have also warned residents in East Watertown to stay in their homes, and not to answer the door unless they see a uniformed police officer outside.
The chaotic incident began with a report of shots fired on the MIT campus at about 10:20 pm (local time) last night, the Middlesex District Attorney's office said. A few minutes later, an MIT campus police officer was found with multiple gunshot wounds in his vehicle. He was pronounced dead at Massachusetts General Hospital, the Boston Herald reported.
Police then received reports of a carjacking at gunpoint by two men in the area of Third Street in Cambridge. The SUV proceeded out Memorial Drive toward Watertown followed by a long train of police vehicles in pursuit.
At one point during the pursuit, the two suspects opened fire on Watertown police and a Transit Police officer, who was shot and who is now in critical condition at a Boston-area hospital.
During the gunfight, the man known as Marathon suspect no 1 was wounded and died in a local hospital. Police have since been searching for the other bombing suspect.
According to the report, the State Police Bomb Squad was removing possible explosive devices believed to have been thrown from the car in Watertowns.