THIS IS KNOWN: On the night of July 23, Don Davis' faithful friend and companion, his dog Bustaah, was shot and killed by a cop. Also known is that Davis, who is homeless, is not friendless. He is surrounded by a caring circle created by Bustaah.

Davis uses the City Hall Coffee House, on South Penn Square, across from City Hall, as his office. Slim and flinty, the 53-year-old Montana native started taking his morning coffee and smokes there about a year ago, after arriving from Atlantic City.

A house painter, he ended up in A.C. after a cross-country odyssey in his camper with Bustaah, hoping to find work. "Bustaah's been all over the United States with me," says Davis with a grin that stimulates a memory, then quickly flees.

It was winter and there was no work in A.C. He was driven to Philadelphia, where opportunity might be better, by a decent, caring A.C. cop, who also gave Davis $20 and a bag of groceries.

Another decent, caring person, coffee-shop manager Cosimo Tricarico, allowed Davis to hang out there with Bustaah, the pair being kind of a fixture in Center City. An ingratiating 3 1/2-year-old, 75-pound Rhodesian blue seal, Bustaah attracted dog-lovers who stopped to pet him. "Everybody loved him," says Tricarico, who fed Bustaah meatballs. "He was the best dog ever."

Petting Bustaah led to conversations with Davis, alone in the world except for his devoted dog. Before long, Davis had a cadre of sidewalk supporters, mostly white-collar professionals who work in the buildings around the coffee shop. Bustaah's Buddies started helping Davis in various ways, like creating a resume for him and giving him a cellphone. They say he refused cash, but accepted food he would share with other homeless people or with Bustaah.

One of Bustaah's Buddies, lawyer David Gaudioso, says Bustaah was friendly, but would show a protective instinct if a stranger approached too fast. When Davis' best friend was killed, lawyer Elissa Katz, one of Bustaah's Buddies, asked me to look into how the dog had died.

Here we get into the unknowns or the untrues.

Davis told me he was walking down Market Street before midnight with Bustaah on a leash. They passed "four or five cops" when Bustaah protectively barked at one of the cops, who pulled his gun and shot Bustaah dead.

Talking with me at the coffee shop, with several of Bustaah's Buddies standing by, Davis says he was beaten at the scene, handcuffed, taken to the Roundhouse, beaten again and turned loose in the morning missing a cellphone and $650 from his pocket.

Police tell a very different story. Their records show that officers responded to a 9-1-1 call reporting an unconscious man with a dog "not letting anyone get near him" at 101 N. Columbus Blvd. That would be near the Race Street Pier, not on Market Street. Police say Davis was drunk and passed out. Fire Rescue was called for Davis, along with the Animal Care and Control Team for Bustaah. Before ACCT arrived, Bustaah got loose and lunged at a cop, who shot him, says police spokesman Lt. Ray Evers.

Davis got the location wrong and has no memory of Fire Rescue being there, but they were, Fire Department records show. He was examined, but not transported. Police took Davis to the 6th District, not the Roundhouse, where Internal Affairs wanted to interview him because a cop's gun was discharged. Davis was too drunk to help, according to Evers. Davis denies he was drinking. He was released in the morning without being charged and with his possessions, Evers says.

If you think a homeless guy with $650 in his pocket seems unlikely, that's a known. The day before the incident, commercial lawyer Susan Verbonitz, one of Bustaah's Buddies, paid Davis $600 in cash for doing a "meticulous" job painting her Phoenixville-area home. Business analyst Dianna Maiorano gave him the cellphone so he could talk with potential employers and has since given him a new one.

Davis claims that police robbed him, but because of major errors in his story — I hate saying this, given the emotional pain over the loss of his beloved Bustaah — his version is not credible.

What happened to his money and cellphone is unknown. They can be replaced. Bustaah cannot.

"Bustaah touched our lives, made our days brighter. What happened is simply terrible — a beautiful, wonderful dog has been killed," Katz says. "A man's life has been devastated."

The final known: A group of Philadelphians, strangers to each other, came together to help a homeless man from Montana. They stand with Davis to this day.

That is Bustaah's legacy.