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SAN FRANCISCO (KPIX 5) — For the last seven weeks, a San Francisco fifth grader has embarked on a physical challenge that most adults wouldn’t consider trying, all of his own accord.

It all began when 10-year-old Niall McDermott watched a movie about a man called the “Iron Cowboy” who completed 50 triathlons in 50 days and was inspired.

“I wanted to do 50 5K’s in 50 days,” he said.

When asked if it was kind of a strange thing for a 10-year-old kid to want to do, McDermott said, “Um, not for me, but for most kids, I think so.”

McDermott’s grandfather was battling lung cancer, and McDermott raised $4,000 in donation pledges.

Fifty days ago, he began his quest when he ran his first 5K near his home in Golden Gate Park. Then, each following day, he ran another 5K. His parents told him that he could quit whenever he wanted, and even they had their doubts that he would continue to run one 5K a day.

“No, I thought it was very unlikely. Ten-year-olds are fantastic, but they embark on a lot of things that they don’t finish,” said Ryan McDermott, the boy’s father.

He said that McDermott had gotten approval from a pediatrician before beginning his epic journey, but nobody thought he would really stick it out to the end.

“He never complained a single day, said he didn’t want to do it, or he’s too tired or something hurt. He was just ready to go every day. I’m amazed. I’ve never really known a kid to do something like this, personally,” said Maggie McDermott, the boy’s mother. “I’m proud to be his mom.”

On Sunday morning’s important run, McDermott was joined by a friend from school. The two joined a local swim-and-run competition to complete his 50th–and final–5K.

As he crossed the finish line, the child who was inspired by the “Iron Cowboy” became an inspiration to himself and others.

When asked what he was thinking as he ran his final 5K, McDermott said, “I was thinking ‘I’m gonna finish this and I can do it, and when I finish it, I won’t have to do it anymore.'”

McDermott’s mother said the experience taught her that all kids–not just her son–are capable of bigger than than we give them credit for.

The funds that McDermott raised will be donated to the Bonnie J. Addario Lung Cancer Foundation in honor of his grandfather.