Boston city is in lockdown as a massive manhunt is now under way to find the teenage suspect wanted for Monday’s bombing that killed three and injured more than 170 people.

The police have identified the suspects as Chechen brothers Tamerlan Tsarnaev (26) and Dzhokhar A. Tsarnaev (19). The eldest brother was shot and killed during a standoff with police on Thursday night but his teenage brother remains at large.

The brothers' father Anzor Tsarnaev told AP in a telephone call from Russia that his son Tamerlan was "a true angel" and that he was a second-year medical student in the US.

A Massachusetts Institute of Technology (MIT) police officer, Sean Collier, has died from the injuries he sustained in a campus shooting with the two suspects last night.

“While the circumstances around the officer’s death remain the subject of an active investigation, what is certain is that the officer gave his life to defend the peace of our campus. His sacrifice will never be forgotten by the Institute. We are thinking now of his family, and our hearts are heavy,” the university said in a statement.

Sean Collier, a 26-year-old Middlesex, Mass. resident was responding to a report of a disturbance when he was shot multiple times. The police officer was found shot in his car and later died at Massachusetts General Hospital. According to the Boston Herald, Collier had only been on the job for a little over a year.

State police spokesman Dave Procopio says the shooting took place at about 10:30 pm outside an MIT building. Cambridge Police Commissioner Robert Haas, said Collier was a dedicated officer who was well-liked by his colleagues and the MIT community.

The events unfolding on Tuesday night after the FBI released the images of two suspects in the Boston Marathon bombings earlier that day.

Shortly after 10pm reports of a robbery at a 7-Eleven store near the MIT campus, in Cambridge, were reported.

At 10:30pm MIT university police officer Collier was found shot in his vehicle. Shortly reports emerged of a carjacking in Cambridge. Police say the suspects commandeered a Mercedes SUV and later released the owner unharmed at a gas station.

At 1am on Friday morning Watertown residents reported hearing gunfire and the sounds of explosion.  Police say the two suspects threw explosives and exchanged gunfire. The ‘black hat’ suspect was wounded and a Massachusetts Bay Transportation Authority officer is shot.  The other suspect fled the area.

MBTA Police Chief Paul MacMillan says the injured officer is 33-year-old Richard Donohue. A three year veteran of the department, he is in surgery at Mount Auburn Hospital in Cambridge.

The injured suspect is taken to Beth Israel Deaconess Medical Center with "multiple traumatic injuries," where he was later pronounced dead.

It is understood the brothers lived together near Boston and have been in the United States legally for about a decade.

Here’s a video of some of the latest reports