Still image taken from video courtesy of NBC shows an explosion at the Boston Marathon, April 15, 2013. [Photo/Agencies]

EVERETT, Wash. - A 78-year-old Washington state man running his third Boston Marathon was near the finish line when he was knocked down by one of two bomb blasts and caught in a news photograph that quickly went viral.

Bill Iffrig, of Lake Stevens, told The Herald of Everett that he heard a noise Monday and found himself on the ground.

"It was only 5 feet away from me," he said. "It was really loud."

He said he ended up with a scrape on his knee, and that a race official helped him to his feet.

Iffrig said most of the other runners near the area weren't as close to the explosion as he was. He walked across the finish line and another half-mile to his hotel. Iffrig said of his proximity to the explosion that it was a "close one" and the experience "scared" him.

The runner's son, Mark Iffrig, of Seattle, told The Associated Press he was tracking his father's race progress online and didn't realize what had happened until he went on Facebook to post about his dad finishing the race. He quickly turned on the TV and called his dad.

"It's horrible. He said it was quite a concussive blast. He was a little dazed. Someone helped him up," said Mark Iffrig , adding he recognized his father from a widely distributed Boston Globe photo showing him on the ground, surrounded by police officers and race officials. "He was only about 10 feet from the finish line."

Iffrig said his father is an avid runner who has raced in a number of marathons.

"He's a hell of a runner," he said. "He's run a lot and he's fast."