Fazzio said she finished the race 15 minutes before the blasts and was standing about 200 yards away. The first explosion caused surprise; but the second left no doubt something profound was happening.
"It was, honestly, like a movie," Fazzio said. "Everyone's legs hurt after running the marathon, but after it happened, everyone was still able to run as fast as they could away from it."
For Nampa marathoner Zachary Dwello, running in his first Boston Marathon, the shock of the first explosion was soon replaced with concern about his father-in-law who was nearing the finish line.
"I heard a really loud boom and a rumble. You could literally feel the ground shake beneath you," said Dwello, a middle school vice principal at Nampa Christian Schools, who said he was standing more than a block away.
"Then I was really worried at that point because I couldn't get a hold of him," he said.
"I just had to pray and hope that he was OK."
Two bombs blew up seconds apart at the finish line of one of the world's most storied races, tearing off limbs and leaving the streets spattered with blood and strewn with broken glass. Three people were killed, including an 8-year-old boy, and more than 170 were wounded.
Federal investigators said no one has claimed responsibility for the violence at a race in which more than 23,000 competed.
Michael Ehredt, 52, of Hope, was among the Idaho residents who made ran the 26.2-mile course and had crossed the finish line when he ran into a friend. Ehredt credits his companion for encouraging him to change out of his wet clothes indoors rather than a corral closer to the location of the first bomb.
"It was all so surreal," said Ehredt. "After I changed, we walked down to the barricade near the finish line, and when we were about a block away, the bomb went off. It was really strange, but everyone was on top of it right away."
For some runners like Rachael Bickerton, of Boise, the act of violence is reason enough to run another Boston Marathon.
"As I was crossing the finish line, I was thinking, 'I'm never going to do this again,'" said Bickerton. "Now, because of this, I may do it again. Boston doesn't deserve this. The streets are just lined with people cheering you. It's the most amazing atmosphere."