Michael Evans immediately goes for his 11-month-old pit bull, Bear, his beloved companion living beneath the rumbling San Francisco Bay Area commuter trains.

“Focus. Sit. That’s my boy,” Evans instructs the high-energy puppy as he eagerly accepts Stewart’s offer.

A quick check of the dog reveals a moderate ear infection that could have made Bear so sick in a matter of weeks he might have required sedation. Instead, right there, Dr. Stewart applies a triple treatment drop of antibiotic, anti-fungal and steroids that should start the healing process.

“This is my son right here, my son. He’s my right-hand man,” an emotional Evans says of Bear, who shares the small RV in Oakland. “It’s a blessing, really.”

“The Street Vet,” as Stewart is known, has been supporting California’s homeless population and their pets for almost a decade, ever since he spontaneously helped a man with a flea-infested dog outside of a convenience store. Since then, Stewart regularly walks the heart of Los Angeles’ infamous Skid Row, giving him a glimpse into the state’s homelessness crisis — and also just how much these people cherish and depend on their pets.

After treating Bear, Stewart hands Evans, a Louisiana transplant, a list of the medicine he provided along with contact information in case the dog needs further treatment. Stewart always promises to cover all expenses.

“It was a good catch,” Stewart said before heading out on his way to the next stop, in West Oakland.

California is home to nearly a third of the nation’s homeless population, according to federal data. About two-thirds of California’s homeless population is unsheltered, meaning they live outside, often packed into encampments in major cities and along roadways. Nationally, up to 10% of homeless people have pets, according to an estimate from the advocacy group Pets of the Homeless. Stewart believes that number is greater.

Homeless shelters often don’t allow pets, forcing people to make heart-wrenching decisions. Stewart sees it as his mission to help as many of them as he can.

A 52-year-old former college hurdler at New Mexico now living in San Diego, Stewart is a lifelong animal lover who grew up in Texas and New Mexico trying to save strays — or at least feed and care for them. He founded Project Street Vet, a nonprofit charity dedicated to helping homeless pets. Stewart funded the group himself for years, saving a chunk of his paycheck before later gaining sponsors and donors.

There’s plenty of heartbreak in Stewart’s work, too. He once performed emergency surgery on a pregnant chihuahua and the two puppies didn’t make it. But more often than not these pet owners are beyond grateful for Stewart’s kindness. He guesses that maybe 1 in 25 times does someone turn down his help.

Stewart hollers “Hello?” outside tents, makeshift structures or campers. He can usually tell there’s a pet if he sees a dog bowl or animal toy. He purposely wears his navy scrub top with his name so nobody mistakes him for animal control or other authorities and feels threatened.

“People are reticent, they don’t always know why I’m coming up to them. If they’re going to you to beg or panhandle, it’s different but if you come up on them they don’t know if you’re law enforcement or you have an agenda,” he said, “so I do take it very slow and I’ll announce myself from afar.”

Approaching Misty Fancher to see if her pit bull, Addie – purchased at a nearby gas station for $200 — might need shots, Stewart offers, “Can she have treats so we can make friends?”

“Sometimes I pull over and just talk,” Stewart explained.

Addie is Fancher’s first pet as an adult, and provides the 42-year-old with some comfort that she is safe living in a relatively unstable neighborhood of Oakland.

“She’s a very good girl,” Fancher said. “She keeps a lot of trouble away. She protects me. She’ll bite someone if they act aggressive or anything toward me. She has before. But she just discourages them from even trying.”

Stewart notices a puncture on the dog’s paw to monitor and also gives her a rabies shot, writing out a certificate for Fancher to keep as proof her dog is vaccinated. He leaves her with tablets for de-worming, treatments for fleas and ticks and — as usual — his contact information.

A little while later, Stewart stops on the outskirts of a park nearby. He walks the perimeter and encounters an RV owned by Eric Clark, who has lived in the same downtown spot for seven years. He has a male bulldog, pregnant pit bull and another pregnant Doberman.

“It’s hard to get to the vet,” Clark said. “I appreciate you. They’re family.”

Stewart is happy he can make a small difference like this with a largely misunderstood community. He strives to treat every person on the streets with the same professionalism and care as he would a patient at his veterinary clinic. His mantra: no judgement, just help.

“They live in the shadows. They live amongst us but not with us,” he said. ” … It is really rewarding. It gets to you a little bit. When they tear up about the tough times they’ve had, you try to care for them, support them.”