The couple's son and granddaughter were unhurt.
A Kansas surgeon had finished the race moments before he ran to help the wounded.
The first blast came about 30 seconds after Dr. Chris Rupe, of Salina, Kan., crossed the finish line. At first, he thought the sound came from a building or grandstand collapsing. He hurried to see if he could help and spent about an hour in the medical tent treating the wounded.
After that, most had been transported to hospital.
"I'd just run 26 miles. I was starting to get tired," Rupe told The Salina Journal. "There were a lot of great people who were there. There are a lot of good people in the world."
Emily Biglin Valentine thanked God she ran a good time.
The Novi, Mich., woman's husband and good friend were in the exact spot of the explosions just a half-hour earlier. They heard the explosions as they walked to a train. It sounded like cannon fire.
"When I finished I was so elated, and I said, 'I'm doing that again.'"
Now she doesn't think she'll go back.
Thomas Fabian II's father had finished the race shortly before the explosions, but his mother was still on the course miles back.
Fabian, of Port Charlotte, Fla., said his mother, Carol, ended up at a cafeteria and chapel on the campus of Boston College with a crowd of other runners. She had a hard time reconnecting with her husband.
Fabian's parents have run nearly 100 marathons in the last five or so years, he said, and were scheduled to fly from Boston quickly to compete in this coming weekend's London Marathon.
"I'm not sure if they're going to go now," he said.
Norwegian Janicke Ekelberg had also finished the race and was walking back to her hotel when she heard the explosions.