<P> On April 18 the Federal Bureau of Investigation (FBI) released images of two suspects, who were later identified as Chechen - American brothers Dzhokhar Tsarnaev and Tamerlan Tsarnaev . The brothers killed an MIT policeman, kidnapped a man in his car, and had a shootout with the police in nearby Watertown, during which two officers were severely injured, one of whom died a year later . Tamerlan Tsarnaev was shot several times, and his brother ran him over while escaping in the stolen car; Tamerlan died soon after . </P> <P> An unprecedented manhunt for Dzhokhar Tsarnaev ensued on April 19, with thousands of law enforcement officers searching a 20 - block area of Watertown; residents of Watertown and surrounding communities were asked to stay indoors, and the transportation system and most businesses and public places closed . Around 6: 00 p.m., a Watertown resident discovered Dzhokhar hiding in a boat in his backyard . He was shot by police while still in the boat and then arrested . </P> <P> During questioning, Dzhokhar alleged that he and his brother were motivated by extremist Islamist beliefs and the wars in Iraq and Afghanistan, that they were self - radicalized and unconnected to any outside terrorist groups, and that he was following his brother's lead . He said they learned to build explosive devices from an online magazine of the al - Qaeda affiliate in Yemen . He also said they had intended to travel to New York City to bomb Times Square . On April 8, 2015, he was convicted of 30 charges, including use of a weapon of mass destruction and malicious destruction of property resulting in death . The following month he was sentenced to death . </P> <P> The 117th annual Boston Marathon was run on Patriots' Day, April 15, 2013 . At 2: 49 p.m. EDT (18: 49 UTC), two bombs detonated about 210 yards (190 m) apart at the finish line on Boylston Street near Copley Square . The first exploded outside Marathon Sports at 671--673 Boylston Street at 2: 49: 43 p.m. At the time of the first explosion, the race clock at the finish line showed 04: 09: 43, reflecting the elapsed time since the Wave 3 start at 10: 40 a.m. The second bomb exploded at 2: 49: 57 p.m., about 12 seconds later and one block farther west at 755 Boylston Street . The explosions took place nearly three hours after the winner crossed the finish line, but with more than 5,700 runners yet to finish . </P>

Who claimed responsibility for the boston marathon bombing
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