John Mixon, an organizer with Run for the Fallen in Maine, was standing on the first row of the bleachers when the first explosion erupted across the street.

“It knocked me right out of the bleachers,” Mixon said. “It was definitely a bomb, you could smell the explosives … you could see the way it blew out that store.”

He and Carlos Arredondo, the father of a fallen soldier for whom a runner was dedicating the race to, sprinted across the street to the blast site and started ripping away snow fence and scaffolding that separated the crowd from the street.

“It was absolutely like a war scene,” Mixon said. “When we got over there, it was just a pile of bodies — people with legs missing.

“They had to be four or five deep on the sidewalk,” Mixon said of the spectators before the bomb went off. “They were all spectators. I don’t think any of the runners got hit at all.”

Arredondo tried using his clothes and towels to staunch the victims’ bleeding but they were hurt too baldly, Mixon said.

Using wheelchairs brought by race medical personnel, they wheeled two seriously injured people to the medical tent.