It was a gruesome end to what should have been a celebration of triumph.
One man's legs were instantly blown off, yet he kept trying to stand up.
Exhausted marathoners had to muscle the energy to flee the bloody scene.
And more than 140 people were hospitalized, some in critical condition.
As authorities try to figure out who triggered the deadly bombings Monday at the Boston Marathon, which killed an 8-year-old boy and two others, many are at a loss to explain why anyone would target the annual event that celebrates thousands of runners from around the world.FULL STORY