Actor Gene Hackman died from heart disease at his home in New Mexico, most likely a week after his wife, Betsy Arakawa, died from the effects of hantavirus, a disease linked to rodents that can cause respiratory failure in rare cases, authorities said Friday.

The revelation that the famous and reclusive couple had died of natural causes put to rest much of the speculation that followed the discovery of their bodies on Feb. 26. But it also raised new questions about the state of mind of Hackman, who investigators said had advanced Alzheimer’s disease, and why the couple was not discovered sooner.

Arakawa, 65, had run a series of errands on Feb. 11, but authorities could find no evidence of any activity after that, suggesting that she could have died that day. Hackman, 95, is believed to have died about a week later, on Feb. 18, according to New Mexico’s chief medical examiner, Dr. Heather Jarrell.Hackman was found on the floor of the mudroom in the couple’s home, near his cane, while Arakawa was found on a bathroom floor, beside a counter with common medication scattered about that investigators later determined did not play a role in her death. They were not discovered until Feb. 26, when a maintenance worker arrived to the couple’s home east of Santa Fe and grew worried when no one answered the door. The worker contacted a security guard, who called 911.

Jarrell said it was possible, given Hackman’s Alzheimer’s disease, that he did not know that his wife had died. It was unclear whether Hackman was able to take care of himself on his own. Autopsies were performed on the couple, Jarrell said, and Hackman’s showed that his stomach was empty, meaning he had not eaten recently, but she said he did not appear to be dehydrated.

Sheriff Adan Mendoza of Santa Fe County said investigators did not find any evidence that Hackman had communicated with anyone after his wife’s death.

While the autopsies answered the most pertinent question of what killed the couple, Mendoza said some aspects of their deaths may remain a mystery, including what Hackman had been doing in the house in the days after his wife died.

“It’s hard to get into the frame of mind of what was happening at the time,” he said. When a reporter asked if it was possible that Hackman had been going to get help when he died, the sheriff said, “I don’t know if we’ll ever have the answer to that question.”

Hantavirus rare and is contracted through exposure to excrement from rodents — particularly the deer mouse in New Mexico. It can cause flu-like symptoms before progressing to shortness of breath, as well as cardiac and lung failure.

People inhale the virus from rodent urine or feces, said Dr. James Lawler, a professor of infectious diseases at the University of Nebraska Medical Center. A patient’s illness can worsen as the capillaries in the lungs become leaky, causing the lungs to fill with fluid. The heart becomes inflamed, and patients may find it difficult to breathe.

Officials said it was unclear from a surveillance video that captured Arakawa around town on Feb. 11 whether she was exhibiting severe signs of illness.

“Most people seek care before they end up at a point where they need the ICU,” Lawler said, referring to a hospital’s intensive care unit.

The infections are rare, but can frequently be deadly. Erin Phipps, a public health veterinarian for New Mexico, said that over the past five years, between one and seven infections have been confirmed in the state annually. But they are often fatal, killing more than 40% of people who have contracted the disease in New Mexico over the past 50 years, she said.

Health department officials found that the couple’s home had a low risk of exposure to hantavirus, but that there were signs of rodents in other structures on the property, which is in a secluded neighborhood overlooking Santa Fe.

Mendoza said Arakawa had gone to a grocery store on the afternoon of Feb. 11 and was also seen on surveillance video at a pharmacy. She returned to the neighborhood around 5:15 p.m., he said, and she did not respond to emails after that day.

Hackman’s autopsy showed severe heart disease, Jarrell said, including evidence of prior heart attacks and multiple surgical procedures involving the heart. He tested negative for hantavirus. She said Alzheimer’s disease was a contributing factor in Hackman’s death.

“He was in a very poor state of health,” she said.

When the couple’s bodies were discovered, officials also found a dog dead in a crate in the home. It is possible that the dog, an Australian Kelpie mix named Zinna, could have died from dehydration or starvation, the state veterinarian said. A necropsy is being conducted on the dog.

Two other dogs, both German shepherds, were found alive on the property.

Zinna had once been a returned shelter dog and had turned into an “incredible companion under Betsy’s hand,” Joey Padilla, the owner of a dog boarder and day care company, Santa Fe Tails, said in a statement this week. Padilla said he had watched Zinna and Arakawa’s relationship “flourish” over the years.

The surviving dogs, Bear and Nikita, are “healthy and receiving the best care in a familiar environment,” Padilla said. He said he was waiting to hear from Arakawa’s lawyer about what to do with them.

Hackman, a two-time Oscar winner, and Arakawa, a classical musician who had founded a home goods store in Santa Fe, had rarely been seen in public in recent years, but when they were spotted in their neighborhood they were often walking their dogs or driving with them in the back.

Neighbors said the couple brightened up when they met a fellow dog lover.

Hackman and Arakawa were known to be private, living at the end of a cul-de-sac in a gated community known as Santa Fe Summit.

Police have said there was no security camera footage from inside or outside the home.

Last week officials said police had quickly ruled out carbon monoxide poisoning, given that both bodies tested negative for the potentially lethal gas.