U.S. Vice President Joe Biden and Massachusetts Governor Deval Patrick will be among top officials attending a memorial service on Tuesday to mark the anniversary of a bomb attack on the Boston Marathon that killed three people and injured 264 others.
The blasts tore through the crowded finish line of the world renowned race, injuring spectators, volunteers and athletes, in the worst mass-casualty attack on U.S. soil since the Sept. 11, 2011 attacks that killed 3,000 people.
This year's race, set for April 21, will take place in an environment of heightened security with the 36,000 runners and tens of thousands of expected spectators facing new restrictions, including bans on carrying backpacks into the race corridor.
Federal prosecutors say that a pair of ethnic Chechen brothers, Dzhokhar and Tamerlan Tsarnaev, carried their homemade pressure-cooker bombs to the finish line in backpacks.
The bombs killed Martin Richard, 8, Krystle Campbell, 29, and Chinese national Lu Lingzi, 23.
Three days after the attack, the FBI released pictures of the suspected bombers and requested the public's help in finding them. That prompted the Tsarnaev brothers to attempt a hasty flight from Boston, which began with them shooting dead Massachusetts Institute of Technology police officer Sean Collier, prosecutors said, in an unsuccessful attempt to steal his gun.
That prompted a police chase that ended in a gunbattle in the Boston suburb of Watertown. Tamerlan, 26, was killed and Dzhokhar, now 20, escaped before being captured on April 19. The brother is awaiting trial on charges that carry the possibility of execution if he is convicted.
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