A Boston Police honor guard is posted outside the Forum restaurant Tuesday, the site of the second of two bombs that exploded near the finish line of the 2013 Boston Marathon. Charles Krupa/AP hide caption

itoggle caption Charles Krupa/AP

A Boston police officer wheels an injured boy down Boylston Street as medical workers carry an injured runner after the Boston Marathon bombing in April. Charles Krupa/AP hide caption

itoggle caption Charles Krupa/AP

Jen Regan strokes the head of her fiancée, Marc Fucarile, as he sleeps in his hospital bed at Massachusetts General Hospital. Fucarile was injured in the bombings at the Boston Marathon, and had to have his right leg amputated. Bill Greene/Boston Globe via Getty Images hide caption

itoggle caption Bill Greene/Boston Globe via Getty Images

April 20 in Watertown, Mass.: Investigators work in and around the boat in which Boston bombings suspect Dzhokhar Tsarnaev was found hiding. Darren McCollester/Getty Images hide caption

itoggle caption Darren McCollester/Getty Images

Some of the graves at the Al-Barzakh Islamic Cemetery in Doswell, Va., where the body of Boston Marathon bombings suspect Tamerlan Tsarnaev has been buried. His grave was not identified to journalists. Yuri Gripas /Reuters /Landov hide caption

itoggle caption Yuri Gripas /Reuters /Landov

FBI Special Agent in Charge Richard DesLauriers (at the microphones), Boston Police Commissioner Edward Davis (standing, at far left) and other authorities briefing the news media on April 19. That's the day Boston bombings suspect Tamerlan Tsarnaev was killed and his brother, Dzhokhar, was captured. Neal Hamberg /Reuters /Landov hide caption

itoggle caption Neal Hamberg /Reuters /Landov

Tamerlan Tsarnaev, as seen in a video taken on April 15 near the finish line of the Boston Marathon. FBI.gov hide caption

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Boston Police Commissioner Edward Davis. Michael Reynolds /EPA /LANDOV hide caption

itoggle caption Michael Reynolds /EPA /LANDOV

This image from a surveillance video, taken near the finish line of the Boston Marathon, helped investigators identify Tamerlan Tsarnaev (in black cap) and his brother, Dzhokhar (in white cap), as the main suspects in the bombings. FBI.gov hide caption

itoggle caption FBI.gov

A video image showing suspect Tamerlan Tsarnaev near the finish line of the Boston Marathon, before the April 15 bombings. FBI.gov hide caption

itoggle caption FBI.gov