Some runners stopped in the middle of the street, confused and frightened. Others turned around and started running back the way they came.
“It is kind of ironic that you just finished running a marathon and you want to keep running away,” said Sarah Joyce, 21, who had just finished her first marathon when she heard the blast.
Bruce Mendelsohn, 44, was at a party in a third-floor office above where the bombs went off. His brother, Aaron, had finished the race earlier.
“There was a very loud boom, and three to five second later, there was another one,” said Bruce Mendelsohn, a US Army veteran who now works in public relations.
He ran outside.
“There was blood smeared in the streets and on the sidewalk,” he said.
Mendelsohn could not be sure how many people had been killed or wounded, but among the bodies he said he saw women, children and runners.
The wounds, he said, appeared to be “lower torso.”
As Melissa Fryback, 42, was heading into the home stretch, she realized she was on pace for one of her best times ever. She steeled herself for the last 5km and finished in 3 hours, 44 minutes. She met up with her boyfriend, and the two had made it about two blocks from the finish line when they heard the blasts.
“I can’t help but wonder that if I hadn’t pushed like that, it could have been me,” she said.