BREAKING: 2nd Bomb To Go Off AT Boston Marathon LIVE FEED

Twitter has been going hot with reporst of not one but 2 bombs exploding at the end of the Boston marathon. 

Spectators covered in blood, and being carried to the medical tent set up for the runners.  Video from the finish line showed screams and an enormous cloud of white smoke.

Will Ritter, the spokesman for a Massachusetts Senate candidate, told NBC News that he heard what sounded like two explosions and saw smoke rising near the Boston Public Library. He said that he saw three fire engines and police running to the site.

“We heard two really large explosions in rapid succession, about a second apart from each other,” Ritter said. “Everybody kind of ducked and hit the ground.”

Janet Wu, a reporter for NBC affiliate WHDH, told NBC News that she heard two loud explosions. Jackie Bruno, a reporter for New England Cable News, said on Twitter that she saw people’s legs blown off.

“Runners were coming in and saw unspeakable horror,” she said.

Massachusetts General Hospital said that it had two patients and was expecting more.

The Associated Press reported that runners and race organizers were crying as they fled the scene.

The Boston police bomb squad was en route. Boston police confirmed there was an incident but did not immediately give details. Police, fire and medical technicians were responding. New England Cable News reported that the emergency response came within seconds.

Federal authorities told NBC News that they had no immediate information.