Knee surgery earlier this year prevented Sonora resident Kyle Stock from achieving his goal of participating in the Boston Marathon for the first time, but the seemingly unfortunate timing might have kept the 39-year-old runner out of harm's way.

Three people were killed and more than 170 injured on Monday after two bombs exploded in the crowded streets near the finish line around the 4-hour mark of this year's race.

"My wife and I think that I would have crossed the finish line around the 3-hour mark," or about an hour before the bombs exploded, Stock said. "I've only been to Boston one time, and we would have probably been mingling or eating around that area."

Stock has been running in the grueling 26.2-mile races for more than a decade, and this year marked the first time he qualified for the Boston Marathon.

Runners qualify for the prestigious race by completing other sanctioned marathons within a certain time depending on their age group. Stock earned his spot after finishing the 2011 California International Marathon in 3:07.

Stock made the difficult decision to stay home this year while still recovering from an operation to his right knee in March. He and wife, Lisa, watched the chaos unfold on television and determined they could have easily been around where the explosions occurred had circumstances been different.

"I feel bad for those people," Stock said.

Stock grew up in Calaveras County and first started running track and cross-country while attending Copperopolis Elementary, where one of his physical education teachers inspired him to one day race in the Boston Marathon.

"It's just been one of those things I've always wanted to accomplish," he said.

Stock ran track and cross-country for the Bret Harte Bullfrogs before graduating from high school and taking a break to pursue other outdoor sports like snowboarding and cycling.

He is active in a number of local sports organizations, including the Golden Chain Cyclists and Tuolumne County Aquatics Masters, and enjoys competing against his wife in local triathlons and marathons.

Stock described the scene near the finish line of any major marathon as crowded and chaotic and sympathized for those caught in the middle of the events in Boston.

"It's hard to find the people you came with after those marathons because you don't have your cell phone with you," Stock said. "So it must have been really difficult for all those runners."

Those close to Stock were already aware of his injury and knew he wasn't in any danger, but a friend called to ask whether the injured competitor was glad he didn't make it to the marathon this year.

Stock said he's never worried about a potential attack at a marathon before, and it won't deter him from chasing his lifelong goal of running the Boston Marathon when he's fully recovered.

"It will be on my mark for probably 2015 or 2016," the determined Stock said. "It's just something I have to do."