U.S. Vice President Joe Biden, along with other leaders and survivors of the Boston Marathon bombing, shared messages of thanks and defiance Tuesday at a tribute to the three people killed and 264 wounded in the attack exactly one year ago.

From Patrick Downes — who lost a leg when a pair of homemade bombs ripped through the crowds at the race's finish line — to Biden, speakers recalled how those on the scene, from police officers to spectators, reacted immediately to help the wounded amid the chaos on April 15, 2013.

Former Boston Mayor Thomas Menino, who managed the response to the attack in the final year of his two decades in office, recalled the struggles of the families of Martin Richard, 8, Krystle Campbell, 29, and Chinese national Lu Lingzi, 23, who died in the largest mass-casualty attack on U.S. soil since Sept. 11, 2001.