A general surgeon from Kansas says he was was helping those with injuries just moments after finishing the Boston Marathon.
Dr. Chris Rupe says he heard a loud explosion about 10 yards away after finishing his run.
Rupe says he headed to what he thought was a building or grandstand collapsing, then heard the second blast.
He was directed to a medical tent where doctors usually help runners with problems like exhaustion.
Rupe spent about an hour treating people mainly with injuries to their extremities. After that, Rupe says, most of the injured had been taken to hospitals.
Rupe's wife, Abbey, had finished the marathon well before the explosions.