A Watertown resident has posted on his blog dramatic pictures taken from his apartment window of the deadly shootout between police and the two Boston Marathon bombing suspects - which took place outside his front door.

Andrew Kitzenberg was working at his computer when he heard "multiple pops coming from outside".

Kitzenberg looked out of his window and saw two people, believed to be Tamerlan and Dzhokhar Tsarnaev, taking cover behind a black SUV while shooting at police.

Kitzenberg took out his iPhone and snapped several shots, not knowing that he was a frontline witness to one of the biggest news stories of the year unfolding before his eyes.

"After witnessing shots being fired I promptly ran up the stairs to my third-floor bedroom to distance myself from the gunfire," Kitzenberg wrote on his blog.

"As I ran into my room, overwhelmed by shock, adrenalin, and curiosity, I jumped on to my bed to stay below the windows but also have a clear view at the shooters and photograph the event."

Kitzenberg said he saw - and pictured - a pressure cooker bomb, similar to those allegedly used in the attack, being detonated.

"I saw them light this bomb," he claimed. "They threw it towards the officers. It created a significant decoy, and there was smoke that covered our entire street.

"While the street was still cloudy with smoke one of the brothers started running down the street towards the officers," Kitzenberg later wrote.

"As he got closer to the officers, within 10-15 yards of them, he was taken down. From my vantage point I did not see whether he was tackled to the ground or brought down by gunshot."

Dzhokhar got in the SUV and forced his way through the police block, Kitzenberg said.

Tamerlan, 26, died in the shootout, while his brother Dzhokhar, 19, was found hiding beneath a tarpaulin in a boat in suburban Watertown after an intensive search by hundreds of police and FBI agents.

Three people, including an eight-year-old boy, died and more than 170 were injured in the Boston marathon bombing.

Dzhokhar is still in hospital in serious conditions because of a bullet fired through his throat and has been charged with conspiring to use weapons of mass destruction. If convicted he could face the death penalty.