A haunting image emerged today showing one of the suspected Boston bombers lurking right behind eight-year-old Martin Richard moments before apparently planting the explosive that killed him.
The suspect, named today as 19-year-old Dzhokhar A Tsarnaev, is seen just feet away from the youngster holding a rucksack believed to contain one of two bombs which killed three and injured 176 others.
Martin had been waiting to give his father a big hug to congratulate him for finishing the race, but never got the chance as the twin blasts ripped through the city centre.
Pictures and CCTV images released in the aftermath of the explosions show how Dzhokhar and his brother Tamerlan Tsarnaev brazenly mingled with the crowds so they could watch the terror unfold before their eyes.
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Moments from death: This chilling image shows one of the Boston bomb suspects standing right behind eight-year-old victim Martin Richard (ringed, left) moments before the explosion
Detonation: The moment the second of the two bombs goes off as hundreds of marathon runners pass by
Shocking: The carnage after bomb goes off on Boylston Street. The picture is blurred because of the graphic nature of the content
Chaos: Tsarnaev is seen calmly walking away from the blast zone as hundreds of spectators and runners run for their lives
The astonishing picture emerged as police and SWAT teams launched a city-wide manhunt today after Dzhokhar went on the run following a fierce firefight with police that left his Tamerlan dead with multiple gunshot wounds.
Blurry CCTV images show the men walking in single file toward the finishing line of the race eastward along Boylston Street at 14.37pm, approximately 13 minutes before the explosions.
Investigators were looking at the men for some period of time before deciding to make the footage public to be sure they could be labelled as suspects, a source said.
Tamerlan Tsarnaev, originally called suspect one, was dressed in a black baseball cap and khaki-colored trousers.
Armed and dangerous: Police are hunting suspected terrorist Dzhokhar A Tsarnaev (left) after he went on the run following a firefight in the Watertown suburb of Boston. The other suspect, his brother Tamerlan Tsarnaev, named (right), died in hospital after the gun battle
Captured on camera: Blurry CCTV images show the men walking in single file toward the finishing line of the race eastward along Boylston Street at 14.37pm, approximately 13 minutes before the explosions
Deadly duo: The brothers head to separate locations where they allegedly planted the explosives
Boston bombing suspects, Tsarnaev brothers, caught on video
How it unfolded: A graphic showing the key locations and chain of events at the time of the blasts
He is seen around five paces ahead of his brother Dzhokhar Tsarnaev, dubbed initially as suspect two, who is wearing a white baseball cap backwards, with a grey hoody underneath a black coat black pants.
In grabs taken from video, the pair do not talk to each other, but move in the same direction with backpacks hanging off their shoulders.
The footage shows Dzhokhar Tsarnaev place down his backpack at the scene of the second explosion just in front of the Forum restaraunt near to where Martin Richard was standing and then move back down Boylston Street in a westward direction.
Video of Dzhokhar Tsarnaev planting his device exists, but the FBI has chosen not to release it because were the media to repeatedly show the suspects leaving the bomb, it might cause some people to overreact if they came into contact with them.
'No more hurting people': In a sad irony, Martin holds up a poster calling for peace in the world before he was killed in the Boston bombings
Wanted: Tsarnaev pictured (left) in surveillance footage while robbing a convenience store after allegedly shooting a police officer on MIT campus late Thursday night and (right) in a poster provided by the Boston Regional Intelligence Center
Carnage: Injured people and debris lie on the sidewalk near the Boston Marathon finish line following an explosion in Boston, Monday, April 15, 2013
'BOSTON BOMBERS ARE FROM CHECHNYA AND HAVE LIVED IN U.S. FOR LAST TEN YEARS'
Dzhokhar and Tamerlan Tsarnaev are believed to be legal immigrants to the U.S., from the Russian region of Chechnya which has been plagued by an Islamic insurgency stemming from separatist wars.
Dzhokhar was born in Kyrgyzstan, according to NBC. His brother Tamerlan was reportedly born in Russia.
The brothers are believed to have moved to America with their family in 2002 or 2003.
The 19-year-old, who attended Cambridge Rindge and Latin School, is an amateur wrestling champion who holds a Massachusetts driving licence.
The older brother Tamerlan attended Bunkerhill Community College and was studying to become an engineer but took a year off to pursue boxing.
A friend of the brothers told CNN that he had known them since 2006 and they were 'normal kids' who partied and occasionally smoked.
The father of the suspects said that his son Dzhokhar is a smart and accomplished young man. Anzor Tsarnaev spoke by telephone from the Russian city of Makhachkala on Friday.
Anzor Tsarnaev said: 'My son is a true angel. Dzhokhar is a second-year medical student in the U.S.
'He is such an intelligent boy. We expected him to come on holidays here.'
Tamerlan Tsarnaev is captured moving through the marathon crowd toward the finish line and scene of the first blast, without his brother suspect two who had disappeared from police view.
A image later emerged of Dzhokhar Tsarnaev calmly walking away from the scene of carnage as runners and spectators fleeing in panic.
The picture taken by Florida businessman David Green came just hours after the FBI lodged an appeal to identify two suspects behind the attacks that killed three and injured over 180.
According to FBI sources who have spoken to CNN, still unreleased footage reveals that Tamerlan Tsarnaev also stayed to watch the devastation.
Hours after the images were made public, the pair killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left Tamerlan Tsarnaev dead and Dzhokhar on the run.
Tamerlan reportedly had a bomb strapped to his chest when he was killed while he and his brother robbed a 7-Eleven, minutes earlier.
Authorities in Boston suspended all mass transit and warned close to 1 million people in the entire city and some of its suburbs to stay indoors as they pursued Dzhokhar, who is believed to have explosives strapped to his body.
Businesses were asked not to open. People waiting at bus and subway stops were told to go home.
From Watertown to Cambridge, police SWAT teams, sharpshooters and FBI agents with armored vehicles surrounded various buildings as police helicopters buzzed overhead.
'We believe this man to be a terrorist,' said Boston Police Commissioner Ed Davis. 'We believe this to be a man who's come here to kill people.'
On his tail: SWAT teams train their weapons toward as house from the roof of a shed as they carry out door-to-door searches for the fugitive terrorist
On his tail: Police search a neighborhood in Watertown, Massachusetts, on the hunt for fugitive Dzhokhar Tsarnaev
SWAT teams later surrounded a house in Watertown following a massive rush of police vehicles through the area.
Dzhokhar Tsarnaev posted online he will 'kill everyone because we killed his brother', according to a dispatcher in Watertown.
Two people have been taken into custody at the home in Cambridge where the brothers grew up but are not considered suspects.
The home is surrounded by FBI and a bomb squad van is on the scene.