"It was awful," said Harmacinski. "Everybody was running away from the smoke, and many of them were covered in blood. It was a confusing and scary scene."
President Obama phoned Gov. Duval Patrick and Mayor Thomas Menino after receiving a briefing from Homeland Security adviser Lisa Monaco on the situation.
"He offered the complete assistance of the FBI and all other federal agencies," the governor told a news conference. "Every resource at our disposal will be used to bring those responsible for this ghastly act to justice."
The president later addressed the nation from the White House press room, saying officials do not know yet who was behind the explosions or why.
"We still don't have all the facts," said the president. "We will get to the bottom of this. We will find who did this and we will find out why they duid this. any responsible individuals, any responsible groups, will feel the full weight of justice."
Obama noted that Monday was Patriots Day, a state holiday in Massachusetts commemorating the battles of Lexington and Concord and the start of the American Revolution more than 235 years ago.
"Boston is a tough and resilient town; so are its people," said Obama. "I'm sure the people of Boston will pull together."
Witnesses to the bombings said the explosions could be heard blocks away from the finish line area. Some said they sounded like cannon fire. Smoke from the bombs spread throughout the area, causing spectators and runners to choke and gag.
Runner Laura McLean of Toronto described a chaotic scene. "There are people who are really, really bloody," McLean said. "They were pulling them into the medical tent."
Cherie Falgoust, who was waiting at the finish line for her runner husband, said the explosions came from a nearby building, perhaps the Lenox Hotel.