tarnaev

A Massachusetts State Trooper makes his way through thousands of chairs before a memorial service for Massachusetts Institute of Technology Police Officer Sean Collier on the Massachusetts Institute of Technology campus in Cambridge, Massachusetts, USA, 24 April 2013. Collier was allegedly shot and killed by Dzhokhar and Tamerlan Tsarnaev on 18 April 2013. Three victims were killed and almost 264 were injured on 15 April 2013 in an apparent terrorist attack near the finish line of the 117th Boston Marathon that prompted a intense manhunt for 19 year old Dzhokhar Tsarnaev who was found hiding in a boat in a backyard.

CJ Gunther/EPA

A Massachusetts state trooper makes his way through thousands of chairs before a memorial service for Massachusetts Institute of Technology police officer Sean Collier on the MIT campus in Cambridge, Massachusetts. Mr Collier was allegedly shot and killed by Dzhokhar and Tamerlan Tsarnaev on April 18. Three people were killed and almost 264 were injured on April 15 in an apparent terrorist attack near the finish line of the 117th Boston Marathon, which prompted an intense manhunt for the two brothers. Nineteen-year-old Dzhokhar Tsarnaev was found hiding in a boat in a backyard.

Holly Holland, right, hugs her daughter Katie, center, as her husband Kevin Holland, left, all of St. Louis,  looks while visiting a makeshift memorial in Boston, Monday, April 22, 2013. The memorial sits on Boylston St., not far from where two bombs exploded near the finish line of the Boston Marathon, Monday, April 15, 2013

Steven Senne/AP

Holly Holland hugs her daughter Katie, both of St. Louis, while visiting a makeshift memorial in Boston, on Monday. The memorial sits on Boylston Street, not far from where two bombs exploded near the finish line of the Boston Marathon, last week.

SWAT teams enter a suburban neighborhood to search an apartment for the remaining suspect in the Boston Marathon bombings in Watertown, Massachusetts April 19, 2013. Police killed one suspect in the Boston Marathon bombing during a shootout and were engaged in a house-to-house search for a second man on Friday in the Boston suburb of Watertown after a bloody night of shooting and explosions in the city's streets.

Jessica Rinaldi/Reuters

SWAT teams enter a suburban neighbourhood in the suburb of Watertown, Massachusetts to search an apartment for the remaining suspect in the Boston Marathon bombings. Police killed one suspect during a shoot-out and were engaged in a house-to-house search for a second man on Friday after a night of shooting and explosions in the city’s streets.