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(CNN) – Megan Gavin-Kirk took up running in 2007 when her husband, Sgt. Josh Kirk, was first sent to Afghanistan. It helped her deal with the stress of his being away and in harm's way.
In 2009, she received the news she had always feared. Her husband, and the father of their daughter Kensington, was killed in action in Afghanistan, defending a remote outpost under enemy attack.
"It was about 10:30-ish in the morning. I normally go for a run in the morning, for some reason I didn't that morning. And I was just watching TV, still in my pajamas, when the doorbell rang," said Gavin-Kirk.
At her door were soldiers bearing the horrible news.
Soon after, she began picking up the pieces, going through her husband's things.
"I was going through paperwork, because there's a ton of paperwork after a death in the military. And I found this folder. There were some papers about future endeavors Josh wanted to do. And I found this little bio in it, and at the bottom it said he wanted to complete the Boston Marathon someday," she says.
Gavin-Kirk has run the Boston Marathon before, but now the race is a mission. Last year, she was prevented from crossing the finish line, stopped at mile 25.
"Prior to that we knew something was going on. Police were saying, 'Go home, go home' to the spectators, and the spectators were saying, 'What do you mean go home?' We didn't know what was going on," said Gavin-Kirk.
Her daughter Kensington was waiting for her mom at the finish line, sitting in the bleachers with her grandmother and uncle.
She heard the bomb blasts.
"I didn't like it," says the 7-year-old.
Mother and daughter were physically alright, but emotionally devastated.
This year Gavin-Kirk came back with new resolve, determined to finish the race that her husband Josh cannot. She is collecting donations in partnership with "Run for the Fallen," an organization that supports families of soldiers lost in battle.
"This year it takes on a whole new (meaning). In coming back, in saying: You're not going to scare us," she says.
Gavin-Kirk finished the race in just over 4 hours and 48 minutes.