Honor guards march after a flag-raising ceremony near the site of one of the two bomb blasts on the one-year anniversary of the 2013 Boston Marathon bombings in Boston, Massachusetts, April 15, 2014. US Vice President Joe Biden, other leaders and survivors of the Boston Marathon bombing shared messages of thanks and defiance on Tuesday at a tribute to the three people killed and 264 wounded in the attack exactly one year ago. [Photo/Agencies]