Police officers with their guns drawn hear the second explosion down the street. The first explosion knocked down 78-year-old US marathon runner Bill...
Runner embraces another woman on the marathon route near Kenmore Square after two bombs exploded during the 117th Boston Marathon on April 15, 2013...
Two officials run away from the first explosion, right, on Boylston Street at the 177th Boston Marathon, April 15, 2013.
In this image released by the Federal Bureau of Investigation on April 19 Dzhokhar Tsarnaev, 19-years-old, a suspect in the Boston Marathon bombing...
Runner reacts near Kenmore Square after two bombs exploded during the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. Two people...
Investigators in white jumpsuits work the crime scene on Boylston Street following yesterday's bomb attack at the Boston Marathon April 16, 2013 in...
Boston Police look at blown out windows at the scene of the first explosion on Boylston Street near the finish line of the Boston Marathon.
Man comforts an injured woman on the sidewalk at the scene of the first explosion on Boylston Street near the finish line of the Boston Marathon.
In this image released by the Federal Bureau of Investigation on April 19 two suspects in the Boston Marathon bombing walk near the marathon finish...
People hug and cry during a vigil for victims of the Boston Marathon bombings at Boston Commons on April 16, 2013 in Boston, Massachusetts. The twin...
Officials react as the first explosion goes off on Boylston Street near the finish line of the 117th Boston Marathon on April 15, 2013.
Emergency personnel respond to the scene after two explosions went off near the finish line of the 117th Boston Marathon on April 15, 2013. Victim...
An injured boy is pushed in a wheelchair by a Boston police officer at the scene of the first explosion near the finish line of the Boston Marathon.
Emily Locher Weston, Connecticut looks out as runners pass near Kenmore Square after two bombs exploded during the 117th Boston Marathon on April 15,...
Person who was injured in an explosion near the finish line of the 117th Boston Marathon is taken away from the scene on a stretcher.
Man is loaded into an ambulance after he was injured by one of two bombs exploded during the 117th Boston Marathon near Copley Square on April 15,...
Boston Marathon bombing hero Carlos Arredondo watches the New England Patriots Super Bowl victory parade on February 7, 2017 in Boston,...
Man sits while police search his car after they found a meat cleaver in it in front of John Joseph Moakley United States Courthouse during the formal...
Investigators stand at the scene of twin bombings at the Boston Marathon on April 17, 2013 in Boston, Massachusetts. The explosions, which occurred...
Woman kneels and prays at the scene of the first explosion on Boylston Street near the finish line of the 117th Boston Marathon on April 15, 2013.
Runners react near Kenmore Square after two bombs exploded during the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. Two people...
Man is loaded into an ambulance after he was injured by one of two bombs exploded during the 117th Boston Marathon near Copley Square on April 15,...
Second explosion goes off as a runner was blown to the ground by the first explosion near the finish line of the 117th Boston Marathon.
Daily News front page April 16 Headline: MASSACRE - At least 3 dead and 140 injured - A woman in tattered clothes looks on in shock amid carnage of...
Close-up of various objects, including flowers, running bibs, and American flags, at a memorial for the victims of the Boston Marathon Bombing ,...
Close-up of flowers around the base of a tree at a memorial for the victims of the Boston Marathon Bombing , Copley Square, Boston, Massachusetts,...
Boston Police officer stands guard at the finish line of the Boston Marathon prior to the flag raising ceremony commemorating the one-year...
In this image released by the Federal Bureau of Investigation on April 18 a suspect in the Boston Marathon bombing walks near the marathon finish...
In this image released by the Federal Bureau of Investigation on April 18 two suspects in the Boston Marathon bombing walk near the marathon finish...
Police clear the bleachers after two explosions went off near the finish line of the 117th Boston Marathon on April 15, 2013.
Member of the bomb squad investigates a suspicious item on the road near Kenmore Square after two bombs exploded during the 117th Boston Marathon on...
First responders tend to the wounded, including a young boy in a wheelchair, where two explosions occurred along the final stretch of the Boston...
First responders load injured people into an ambulance where two explosions occurred along the final stretch of the Boston Marathon on Boylston...
Athletic gear, including boxing gloves, skis, numerous sneakers and a basketball was found inside Tamerlan and Dzhokhar Tsarnaev, 3rd floor apartment...
Daily News front page April 24 Headline: KILLER DEAL - Bombers paid for lethal explosives - got 2nd set FREE - Tamerlan and Dzhokhar Tsarnaev used...
April Walton, manager of Phantom Fireworks store in Seabrook, New Hampshire, where Tamerlan Tsarnaev used a buy one, get one free coupon to buy two...
Police block road after a campus police officer at Massachusetts Institute of Technology was shot near Building 32 during hunt for two suspects in...
Close-up of various objects, including flowers, a dreamcatcher, dog tags, and wind chimes, at a memorial for the victims of the Boston Marathon...
Close-up of flowers, including forsythia and a rose, in a plastic gallon jug at a memorial for the victims of the Boston Marathon Bombing , Copley...
View of people with umbrellas in a partially enclosed, plastic-covered memorial to victims of the Boston Marathon Bombing , Copley Square, Boston,...
Close-up of various objects, including flowers and American flags at a memorial for the victims of the Boston Marathon Bombing , Copley Square,...
Close-up of various objects, including T-shirts, flowers, rosaries, prayer flags, and a glow stick, at a memorial for the victims of the Boston...
Close-up of a plastic-covered message at a memorial for the victims of the Boston Marathon Bombing , Copley Square, Boston, Massachusetts, May 9,...
View of a partially enclosed, plastic-covered memorial to victims of the Boston Marathon Bombing , Copley Square, Boston, Massachusetts, May 9, 2013....
Close-up of various objects, including T-shirts, flowers, and American & Puerto Rican flags, at a memorial for the victims of the Boston Marathon...
Close-up of running shoes hanging on a plastic-covered memorial to victims of the Boston Marathon Bombing , Copley Square, Boston, Massachusetts, May...
View of a partially enclosed, plastic-covered memorial to victims of the Boston Marathon Bombing , Copley Square, Boston, Massachusetts, May 9, 2013....
Close-up of messages written on 'One Boston' leaflets and posted at a memorial for the victims of the Boston Marathon Bombing , Copley Square,...
Close-up of flower arrangements and American flags at a memorial for the victims of the Boston Marathon Bombing , Copley Square, Boston,...
View of a running shoe at the base of a plastic-covered memorial to victims of the Boston Marathon Bombing , Copley Square, Boston, Massachusetts,...
View of a plastic-covered memorial to victims of the Boston Marathon Bombing , Copley Square, Boston, Massachusetts, May 9, 2013.
Close-up of messages written on 'One Boston' leaflets and posted at a memorial for the victims of the Boston Marathon Bombing , Copley Square,...
Close-up of flowers and American flag, among other items, on and around a tree at a memorial for the victims of the Boston Marathon Bombing , Copley...
Close-up of various objects, including a T-shirt, flowers, rosaries, prayer flags, and a glow stick, at a memorial for the victims of the Boston...
View of a partially enclosed, plastic-covered memorial to victims of the Boston Marathon Bombing , Copley Square, Boston, Massachusetts, May 9, 2013....
View of running shoes hanging on a plastic-covered memorial to victims of the Boston Marathon Bombing , Copley Square, Boston, Massachusetts, May 9,...
View of various objects, including T-shirts, flowers, a paper crown, and American flags, on and around a tree at a memorial for the victims of the...