Police were spotted with their guns drawn after two explosions took place at the sight near the finish line of today's Boston Marathon.  Three  people are dead, 140 people have been injured, several critically according to updated reports.

It was a scene of people covered in blood being wheeled away in chairs and gurneys as investigators continue to search for the cause of the blasts which took place shortly after 3 p.m. Monday.

So far officials will not confirm the bomb as a terrorist attack, though two other devices have been located by firefighters and are being dismantled.  CNN.com confirmed a third explosion happened at the John F. Kennedy Presidential Library at approximately 4:30 p.m. about 5 miles southeast of the Boston Marathon finish line.

President Barack Obama is reported to have reached out to the Mayor of Boston to offer assistance.

Sports producer Steve Silva told Boston.com  "I saw blood everywhere. It was just an explosion, it came out of nowhere," he said. "There are multiple injuries. I saw dismemberment, I saw blood everywhere. People are badly injured."

Boston Globe reporter Cynthia Needham tweeted from the scene:

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