One suspect in the Boston Marathon bombing was shot dead in a firefight with the police in the Watertown area, while another one remains on the loose, BPD confirmed.

The firefight, which involved explosives, ensued after an MIT police officer was shot and killed on Friday morning, and fellow officers followed the lead of an apparent carjacking.

The killed suspect was wounded during the gun exchange with the police and was apprehended, police said. He later succumbed to the injuries.

The suspect remaining at large is the FBI’s Suspect 2 in the Boston Marathon bombing, the so-called ‘white hat suspect’. Police called the man a terrorist, who is armed and dangerous.

A 20-block perimeter was established as the manhunt for the second suspect continues. Unconfirmed reports citing police dispatch say the dead suspect had explosives strapped to his person and that the one on the run may have a similar device.

Officials from the Beth Israel Hospital, where the wounded suspect was taken, say the man had gunshot wound and other injuries, likely sustained in an explosion. They didn't ID the diseased person.

The police did not release the names of the suspects they confronted in Watertown.

The FBI has released four more pictures of the Marathon bombing suspects, showing their faces from the front. 

Photos released by FBI

Earlier the bureau published several pictures and a video of the two suspects.

Photos released by FBI

Positive subject identification

Jeff Bauman, the Boston Marathon victim whose grisly injury was replicated by photo-hungry news agencies, was the first person to identify a suspected bomber to the FBI.

"He woke up under so much [sic] drugs, asked for a paper and pen and wrote, ‘bag, saw the guy, looked right at me,’" his brother, Chris Bauman, told Bloomberg.

“I’ve had many times with him alone, and yes, he told me every detail.”

Bauman had been standing near the finish line waiting for his girlfriend to complete the Boston Marathon when a man wearing a baseball cap, dark jacket and sunglasses dropped a bag at his feet, according to his brother Chris Bauman.

Less than three minutes later the bag detonated, with the blast mangling both of Bauman’s legs.

While still in intensive care Bauman, 27, spoke with FBI agents and helped in the identification of the possible perpetrators – the same faces that investigators asked the public to help identify during a press conference on Thursday afternoon.

He has survived the attack but both limbs were amputated below the knee. The man Bauman saw with the bag has since been identified as one of the Federal Bureau of Investigation’s two suspects in the bombing that killed three people and injured nearly 200 more.

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