Manhunt: Boston Bombers

NOVA: On 15 April 2013, two bomb blasts turned the Boston Marathon finish line from a scene of triumph to one of tragedy, leaving three dead, hundreds injured and a city gripped by heartbreak and terror. Less than five days later, the two key suspects were identified and apprehended with one dead and the other in custody. How did investigators transform the chaos of the bombing into a coherent trail of clues pointing to the accused killers?