The man who fell to his death down a Brooklyn stairwell while taking two pooches out for a stroll was in town from Massachusetts and doing it to help out his long-distance girlfriend’s dog-walking business, the woman said Friday.

Christian Dallett, 53, a web designer and father of two, had previously cared for the pit bull and mixed-breed dog — named Frank and Honey Pie — when he lived in the borough and wanted to walk the two pooches while he was in town for the weekend, said his girlfriend, Carol West.

“We both had been taking care of those dogs since [the owners] got them, so he knows them inside and out,” West said of her boyfriend of five years.

“He wanted to see some of the dogs he had taken care of over the years,” said West, who gave her regular dog walkers Thursday and Friday off so Dallett, who goes by the nickname CJ, “could walk some of his familiar dogs.”

She added, “He would walk dogs if I needed help.”

Dallett was inside the client’s building on Carroll Street in Red Hook at 5 p.m. when cops believe the pooches overpowered him, causing him to fall down the stairs and hit his head, killing him.

West believes that Dallett may have simply “tripped” to his death.

“He may have tripped on the stairs while walking the dogs,” West said. “I’m trying to deal with this. This is devastating for me.”

West was nearby when she got the phone call from the dogs’ owners about Dallett’s tragic fall and ran over to the building, where she found him at the bottom of the steps, she said.

“It looked like he fell. I walked right in there,” said West, adding that the dog owners’ young son first made the discovery.

“It was devastating for [the owners] too because her son opened the door and saw him at the bottom of the stairs,” she said.

The Medical Examiner’s Office ruled that “The cause of death is blunt trauma of head. The manner of death is accident.”

Dallett, a longtime Brooklyn resident who moved from the borough to the Berkshires in October to care for his mother, leaves behind two teenage daughters.

“He loved his daughters more than anything. He helped them to be intelligent and strong,” Dallett’s ex-wife, Melissa Dallett, 52, said of one of her “oldest friends.”

Melissa and their children, Anais, 13, and Liliana, 19, were on their way to meet Dallett when they got the terrible news.

“He was a writer. He was in the middle of writing a memoir,” a heartbroken Anais said.