Los Angeles (CNN) -- Darrel Folkert of Redondo Beach, California, stood next to a mailbox near the finish line of the Boston Marathon to cheer on his wife as she completed the race.
Moments later he was suddenly thrown by a loud explosion that shattered windows behind him, lifted tables from their foundations and tossed chairs along the sidewalk.
"He was standing right next to the mailbox when it exploded," his wife, Jac Bost, told CNN in a phone interview.
The mailbox, one of the only objects left intact after the second explosion and the site where authorities have focused their investigation, may have saved Folkert's life. He suffered non-life-threatening puncture wounds to the leg and returned last week to Los Angeles, where he is recovering, Bost said.
Folkert and Bost, both 42, are avid ultra-marathon runners, competing in events with distances of up to 50 miles.
Bost, a marketing executive, was competing in her seventh Boston Marathon and was less than a quarter mile away from the finish line when she heard a loud boom. She said organizers stopped her as word spread of an explosion and people began frantically running away from the scene.
At first, she did not know what had happened to her husband, but strangers lent her a phone so she could contact him.
Meanwhile, two men carried an injured Folkert to a nearby store, where they called 911 and lent him a phone to call relatives, she said.
"It was the extreme generosity of people of Boston who offered to help that deserve the praise in the aftermath of what happened," she said.
Folkert, who is expected to fully recover, and Bost are hoping to locate the two men who treated him at the scene and the others who helped them reunite, Bost said.
"Everyone in the city of Boston was phenomenal, and I can't understate the level of generosity we received," she said.