On July 1, Kent Green, a police officer in Mesa, Arizona, began receiving messages from people who said they had seen his photo on Facebook. Not knowing what they were talking about, he didn’t know if he should be concerned. Then he learned that a local citizen had caught him in an act of kindness.

Green had been driving by a dumpster and saw a man inside, who was collecting cans and bottles. Green stopped to ask him to get out, out of concern for his safety.

“We’ve had some deaths from people either falling asleep or camping out in a dumpster, or behind, and then the garbage vehicle comes out and it can end really badly,” Green told Runner’s World by phone.

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As Green turned to leave, he noticed that the man might benefit from a new pair of shoes, so he asked him if he’d like to try a pair on. Green grabbed one of the many pairs of running shoes he carries in the back of his patrol car, and the man gladly took them. Unbeknownst to both parties, they had an audience.

Green didn’t think twice about it, but by the following day, local resident Jenny Crider’s post about his act had gone viral. The Mesa Police department shared the post and explained that Green is a competitive runner.

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Green, 28, has been a police officer for eight years, and has been giving away his old running shoes in this manner for several years. During his peak training, the ultramarathoner runs 70 to 80 miles per week, which can mean he goes through a pair of running shoes in 4 to 6 weeks. As a result, he winds up with many pairs of slightly used running shoes, which still have plenty of life left in them.

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While patrolling, Green often sees people who are barefoot, which can be particularly challenging in the Arizona summers “when you can pretty much boil an egg on the concrete,” he said. Green realized that he could put his size 10.5 shoes to good use.

A high school soccer player, Green ran his first marathon nearly 10 years ago. Just over a year after that, he ran his first ultramarathon and has been hooked ever sense. He has a marathon best of 2:54:45 from the 2014 Tucson Marathon, and is hoping to run the Man Against Horse 50 Miler for the third time in October.

Though Green had told some other officers about the shoes—they’d ask why he was carrying a garbage bag full of sneakers in the back of his patrol car—his donations were mostly a private act. Until now.

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Green said that many other officers do similar things, he just doesn't know others who give out running shoes.

“[Some] pack hygiene kits, they’ve bought hotel rooms for families, they’ve bought food, baby supplies,” Green said. “It’s endless what goes unseen.” 

Since his recent attention over his donation, Green has heard from many people who want to contribute shoes for him to hand out.

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“It’s been overwhelmingly positive, humbling, and just awesome,” he said, but noted that his patrol car is only so big. But he hopes that this will inspire people to directly help others in need in a similar spirit. He also hopes it will shed some light on the many things police officers do for their communities.

“I just hope [this] brings a little positivity to police and what they do behind the scenes every day, every night,” Green said. “It’s not particular to Mesa, it’s not particular to Arizona. It’s everywhere.”

This article originally appeared on RunnersWorld.com.