The man who became the bloodied face of the victims after the Boston bomb attacks provided the key identification of the dead suspect.
Jeff Bauman was waiting to see his girlfriend finish the race when a man dropped a backpack at his feet. Mr Bauman (27) lost both his legs in the explosion. Despite being heavily drugged, Mr Bauman got word to the authorities that he had seen one of the bombers.
He told FBI investigators that he looked in the eyes of Tamerlan Tsarnaev as he planted the bomb. He went on to identify him in a photograph.
Mr Bauman's brother, Chris, said: "He woke up under so much drugs, asked for a paper and pen and wrote, 'bag, saw the guy, looked right at me'."
As Mr Bauman was treated in intensive care, he was interviewed by FBI agents and gave a description of the bomber.
His brother said the account was emphatic and convincing. "I've had many times alone with him, and yes, he told me every single detail," Chris said.
The FBI was able to narrow its inquiries down to two suspects from thousands of people pictured in the area before the attacks. The information triggered the manhunt that culminated in the shoot-outs that shut down Boston.