Katie Newhouser regularly delivered packages to Leo's former owner's condo complex, which is how they first became friends

A dog named Leo’s life story went from tragic to triumphant when a caring UPS driver named Katie Newhouser from Rancho Cucamonga, California, crossed paths with him.

In May, Newhouser posted a photo of her pit bull pal in a Facebook group called UPS DOGS. Their bittersweet tale touched many hearts and began to garner attention.

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As she writes in her post, Leo’s “owner passed away and now he lives with me.” That’s the short version of the story; the more in-depth tale, as first recounted by Newhouser to Pup Journal, is more dramatic and heart-tugging.

Leo had been adopted by his original owner, a woman named Tina, after her son Cannon brought him home as a puppy. Leo was actually too young to have been separated from his dog mom, so he could not yet eat solid puppy food and Tina had to bottle-feed him. Thus, the pair formed a unique bond.

“They were very very close and did everything together,” Newhouser tells PEOPLE. “I don’t think that dogs ever forget anyone who they have been that close to.”

Image zoom Katie Newhouser Facebook

The friendly pup also bonded with his local UPS driver, Newhouser. She tells Pup Journal, “He would hear my truck come into the condo complex and start barking and scratching at the door to come down to the truck. He would love to come into the truck and go into the back to look around. I remember one day I was driving up one of my busier streets and they were coming down the street and all of a sudden there was Leo popping his head out the passenger side barking at me! He barked all the way down the street!”

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Newhouser learned of Tina’s untimely death through a Facebook post. She contacted her friend’s son Cannon, a Marine who could not keep the dog, and offered to foster Leo. Although Newhouser already had three pups of her own, her personal bond with Leo proved too strong to let go of the gentle giant.

Image zoom Katie Newhouser Facebook

“It was probably confusing for him at first, [but] he has adapted well,” says Newhouser. “He and his brother Moose are inseparable. Bailey, his sister, has taken a while to come around, [but] they actually play now … once Leo was introduced into the house, the whole vibe changed.”

Image zoom Katie Newhouser Facebook

“He loves going for rides, he loves the water, he loves playing with his chew toys, he loves tormenting his two feline sisters, he loves laying in the sun, he has NO concept of personal space. He likes to be on us or right beside us! He is a character,” says Newhouser of her new furry kid.

One new lifestyle challenge for Leo was weaning him off the human food that Tina used to feed the pup. His begging face was in full effect 24/7. However, Newhouser adjusted by adding boiled chicken to all her pups’ dog food, which she figures may partially account for the rest of the canine crew accepting him with open paws.

Image zoom Katie Newhouser Facebook

“He has some health issues,” Newhouser tells PEOPLE. “He has had constant ear infections since he has been here, and he has also developed a really bad rash. We recently found a really good vet and she is trying new treatments on his ears and seems to think he has a food allergy, so we have switched all their food over to limited ingredients to see if that helps.”

However, the biggest challenge for Leo was more emotionally focused.

“Leo missed Tina when he first got here,” Newhouser explained to Pup Journal. “He would whine at night before he would fall asleep. It was heartbreaking, really. He still does every once in a while. I know he misses her.”

Despite his moments of sadness, Leo has come a long way and absolutely loves playing with his new dog siblings. While neither Leo nor Newhouser expected that a twist of fate would bring them together permanently, it’s a sweet relief to know their friendship has blossomed into a forever family.