Before Gene Hackman faded from public view in his adopted hometown of Santa Fe, N.M., the locals would see the aging movie star on the golf course or in his truck or walking his beloved dogs in the enchanted western city, amid the mesquite, juniper and pinyon pine.

His wife, Betsy Arakawa, was often alongside him. There was much about his life that she managed. She set up the golf games with his friends. She policed his diet, given the heart trouble that had dogged him for decades. She diluted his wine with soda water. She typed and edited the novels he wrote by hand.

She also apparently took on the role of sole caregiver as he endured the devastating effects of Alzheimer’s. Thirty years his junior, she must have planned to see him to his end, in their home.

And so it was all the more jarring on Friday when authorities in New Mexico revealed more dark turns in the mystery of how the couple died last month in their four-bedroom house, hidden by trees at the end of a luxurious cul-de-sac east of the city.

Officials said the couple died of natural causes, he of heart disease and she of a rare viral infection. But it was Ms. Arakawa — the caregiver, lover, protector — who died first, perhaps on Feb. 11, leaving Mr. Hackman, 95 years old with advanced Alzheimer’s, alone in the house for days. He is believed to have died a week later, on Feb. 18.

Their decomposing bodies were not discovered for yet another eight days, when a maintenance worker called a security guard to the house after no one came to the door. Emergency workers found Ms. Arakawa, 65, on the floor of a bathroom near a medicine bottle and spilled pills. Zinna, one of their three dogs, was dead in a crate in a closet. The body of Mr. Hackman was discovered in a mud room, with slippers and a cane.

New Mexico’s chief medical examiner said on Friday that Alzheimer’s disease was a contributing factor in Mr. Hackman’s death. Ms. Arakawa died of hantavirus, which is contracted through exposure to excrement from rodents, often the deer mouse in New Mexico.

The exact details of what happened in the house over the course of that week may never be known. Friends and neighbors said that the couple had increasingly receded into the private confines of their hillside house since the onset of the Covid-19 pandemic.

But the timeline presented Friday raises the terrifying possibility that Mr. Hackman, a Marine veteran and actor of consummate precision and control, had spent days in the presence of his fallen wife, too disoriented or feeble to call for help — trapped, essentially, in the handsome, secluded home that had been his reward for a life toiling in the limelight.

Mr. Hackman was drawn to Santa Fe in the late 1980s, shortly after his divorce from his first wife. He had already earned an Oscar for his starring role in the 1971 thriller, “The French Connection.” Another Oscar, as a supporting actor in the 1992 western “Unforgiven,” would come later.

His father, who abandoned the family when Mr. Hackman was 13, was a pressman for the local newspaper. His mother was a waitress. But Mr. Hackman had a bohemian streak, and he was drawn to Santa Fe’s stunning natural landscape and the artists the landscape inspired. He would become one of them, spending much of the second half of his life painting, sculpting and writing fiction in Santa Fe, far from the trophy homes of Beverly Hills that many celebrities of his caliber inhabit.

Ms. Arakawa was a classical pianist, born in Hawaii. She met Mr. Hackman in Los Angeles at a fitness center where she had a part-time job. He had forgotten his entry card, and she refused to let him in, according to Rodney Hatfield, a friend. They married in 1991. Friends said that the relationship seemed natural, despite the age difference.

“That part never came to mind because they seemed equal in so many ways,” said a friend, Susan Contreras. “She was a personality unto herself.”

The life they settled into in Santa Fe was both charmed and strikingly normal. Architectural Digest featured an earlier hilltop house they owned outside of town, built to their specifications in an elegant Southwestern style. Mr. Hackman joined the board of the Georgia O’Keeffe Museum, one of the city’s storied cultural gems. They invested in a restaurant, Jinja, which displayed Mr. Hackman’s paintings and named a house mai tai cocktail in his honor.

But others remembered a man who often seemed to fit the mold of the Everyman he so often played onscreen. Helen Dufreche, a former neighbor, recalled meeting Mr. Hackman for the first time about a decade ago. He was wearing a baseball cap and had pulled up alongside her in a truck to compliment her dachshunds.

“What cute puppies!” he said.

Tom Allin, a longtime friend of Mr. Hackman’s, said Ms. Arakawa had always served as something of a gatekeeper for her famous husband. Over a 20-year friendship with Mr. Hackman, Mr. Allin never recalled speaking to him over the phone or emailing with him. He would always set up golf games or visits through Ms. Arakawa. Uninterested in technology, Mr. Hackman did not have a cellphone that Mr. Allin knew about.

“She was very protective of him,” Mr. Allin said, adding that Mr. Hackman seemed happy to have his wife run things.

He recalled Mr. Hackman saying that he would have been dead “long ago” without his wife taking care of him and ensuring that he ate healthily.

In January 2020, just before the pandemic, Mr. Allin said, he saw his friend for his 90th birthday in Islamorada, Fla. He recalls Ms. Arakawa mixing soda water into his wine. “She just really looked after him,” he said.

He also said that he could sense that Mr. Hackman was declining. The couple had a tradition where Mr. Hackman would cook dinner each year for Ms. Arakawa’s birthday. In 2023, she came home expecting a meal, Mr. Allin recalled, but Mr. Hackman had forgotten their ritual.

Like many older Americans, Mr. Hackman retreated indoors during the Covid crisis to stay safe. In recent years, neighbors in Santa Fe Summit, the gated community where the couple lived, said they had seen no sign of the couple, except for their trash cans on the side of the road, waiting to be picked up.

During Friday’s news conference, Sheriff Adan Mendoza of Santa Fe County said that investigators had determined that on Feb. 9, a Sunday, Ms. Arakawa had picked up Zinna from a veterinarian after the dog underwent a procedure, which could explain why Zinna was being kept in a crate.

On Feb. 11, perhaps hours before she died, Ms. Arakawa emailed her massage therapist in the morning and then went to a grocery store in the afternoon. She was also captured on surveillance video making a brief stop at a pharmacy. Sheriff Mendoza said he believed she wore a mask that day while in public, which she often did to avoid bringing any illnesses back to her husband, friends said.

Ms. Arakawa stopped by a local pet food store later that afternoon and then returned to her neighborhood around 5:15 p.m., the sheriff said. She did not respond to any emails after that day.

Asked whether the couple had anyone taking care of Mr. Hackman, Sheriff Mendoza said, “At this point, there’s no indication that there was a caretaker at the home.”

James Everett, who lived part-time in the neighborhood for about five years, said in an interview last week that he found it unusual that the couple did not have any caretakers, given Mr. Hackman’s age. “I know when my dad was 95, 96, 97, 98, we had a live-in cook and maid for him,” he said. “I’m surprised they didn’t have them.”

Another neighbor, Robert Cecil, wondered whether the couple’s desire for privacy was, in the end, a “weakness” that contributed to the horror that befell them.

But Mr. Hatfield, Mr. Hackman’s longtime friend, said that Mr. Hackman loved Santa Fe because it allowed him to live a life that was not always that of a star. “I know that Gene did not like the role of celebrity,” he said. “It was pretty obvious.”

Another friend, Stuart Ashman, said that solitude was often the goal for people who migrated to Santa Fe. “People come here as a way to hide out,” he said. “They certainly did.”