The Boston police officer shot and wounded during a fierce gunfight with the Boston marathon bombing suspects lost all of his own blood and his heart stopped beating for a shocking 45 minutes before he was successfully resuscitated, his doctors say.

Massachusetts Bay Transportation Authority Officer Richard 'Dick' Donohue Junior, 33, is now expected to make a full recovery according to his surgeon, Doctor Russell Nauta.

Donohue, an Irish American husband and father, responded to a call for assistance at the scene of an earlier shooting at the famous Massachusetts Institute of Technology (MIT) campus when a gun battle erupted with the suspects and he was shot in the leg.

A bullet severed his femoral vein and artery, leading to rapid blood loss, doctors said.

Tragically the MIT officer whom the suspects had earlier shot and killed was Officer Donohue's friend, Sean Collier. Donohue and the slain MIT officer graduated from the police academy together in 2010.

On Monday Doctor Nauta told the press that Donohue's heart had stopped for more than 45 minutes before doctors were finally able to restore his pulse. A surgical team was able to stop the bleeding in time to save his leg. Doctors are reportedly optimistic that he will make a full recovery and be able to walk again.

'Signs are positive and we are hoping for a speedy recovery,' Edward Donohue, the officer's brother, told the press. 'Dick loves being a cop — we were just talking the week before about how much he loves the job,' Donohue said.

The Tsarnaev brothers ambushed Collier when he responded to a disturbance on the MIT campus late on Thursday night, three days after the deadly blasts at the Boston Marathon. He was hit possibly five or six times. His gun was still in the holster.

'These are the bravest men and women I know,' Collier’s stepfather Joe Rogers said at Saturday’s vigil. 'Every day they go out to keep us safe from the people who do evil in the world," Rogers said. "I think we need to applaud them because one night it could be them walking down a dark alley.'