Bill Iffrig is an avid runner who has completed more than 40 marathons. The 78-year old was just about to finish his third Boston Marathon on Monday afternoon when the first of two bombs exploded, knocking him off his feet.
"I had just come around the last corner, heading for the finish line. I was within 15 feet of the finish line and all the sudden this blast went off, and oh my God it was so loud," he said.
The moment, which was captured on video and broadcast around the world, shows Iffrig and dozens of other runners approaching the finish line when a giant fireball erupts.
The wave of energy hits Iffrig and sends him to the pavement.
"I didn't even have time to think about what it was about. My whole body started getting woozy and my legs were wobbling and I knew I was going to hit the deck," he said.
Even in the shock of the moment, Iffrig said he knew a bomb had gone off. As he lay on the ground, he said he could see parts of the bomb scattered around him.
"I was pretty sure it was a bomb of some sort," he said. "I was pretty sure of that, but I had no idea it was terrorism. I didn't have time to think about it, I guess."
Somehow, Iffrig was not injured in the blast, save for a skinned knee. He was checked out by nearby medics and sent back to his hotel. Iffrig said he and his wife will fly back home on Friday.
At least three people were killed and more than 130 were injured in the blasts.