A day of triumph and achievement, shattered in moments.
In a press conference at the White House Tuesday, President Obama called it "a heinous and cowardly act."
"The FBI is investigating it as an act of terrorism," said Obama.
Three people killed, including an 8-year-old boy, and more than 170 injured after two bombs blew up seconds apart at the finish line of the Boston Marathon. Marquette native/resident Kylie McAuliffe was at the race. She missed the initial explosion, but witnessed the aftershock, which she described as the scariest moment in her entire life.
"I was in the middle of all this chaos and everybody??s screaming, 'It??s a terrorist attack!'" said Kylie. "There are dead bodies, there??s blood, there??s people everywhere."
"You just look around and there??s fear in everybody??s faces," she added.
The Boston Marathon is one of the most prestigious races in the world, and this year had over 23,000 athletes.
Marquette resident Jeri Mommaerts ran the marathon last year, calling it an incredible accomplishment. And for runners there Monday, now a lifetime dream destroyed.
"The people that trained for months, years, to qualify to be there," said Mommaerts. "Then such innocent people, innocent bystanders...it makes me very angry to think that someone would do this."
But authorities are still in search of clues for who's behind the explosions that sent thousands racing for safety.
"We will go to the ends of the earth to identify the subject or subjects who are responsible for this despicable crime," said Richard DesLauriers, the FBI agent in charge in Boston. "We will do everything we can to bring them to justice."