Actor Gene Hackman was alone.

The two-time Academy Award winner didn’t make any calls and missed meals.

Medical experts say it’s possible the 95-year-old, who was in declining health and suffering from advanced stages of Alzheimer’s disease, did not even realise his wife of more than 30 years was dead in the home where he was living.

If he did, experts told the BBC, he likely went through various stages of confusion and grief, trying to wake her up before the disease caused him to become distracted or too overwhelmed to act – a process that likely repeated for days before he, too, died.

Officials in New Mexico say Betsy Arakawa, 65, died of a rare virus about seven days before Hackman perished on 18 February of natural causes.

The pair – and one of their dogs – were found dead in their Santa Fe home after neighbourhood security conducted a welfare check and saw their bodies on the ground through a window.

Authorities, at first, said the grim discovery was “suspicious enough” to launch an investigation.

Their remains were discovered in advanced stages of decomposition. Arakawa was found in a bathroom with scattered pills nearby. Hackman was found near the kitchen with a cane and sunglasses. One of their three dogs was found dead in a crate.

But a police investigation found no foul play.

Instead, the case has shed light on the grim realities of Alzheimer’s disease, which damages and destroys cells in one’s brain over time – taking away memory and other important mental functions.

“It’s like he was living in a reel,” Catherine V Piersol, an occupational therapist with decades of experience in dementia care, told the BBC of how Hackman may have experienced the repeated loss of his wife.

She noted patients with advanced Alzheimer’s disease like the actor live in the present and are unable to both look back at moments in the past or look forward and act.

“I imagine he would be trying to wake her up and not being successful. But then [he] could have been distracted in another room because of one of the dogs or something,” she described.

Then later, he’d again notice his wife on the ground and would “live through it again”, she said.

Though no one knows how Hackman spent his last days alive, the grim nature of the possibilities were discussed by authorities and the area’s medical examiner.

At a press conference last week, Dr Heather Jarrell, New Mexico’s chief medical examiner, said Arakawa died of hantavirus pulmonary syndrome (HPS), a respiratory illness caused by exposure to infected rodents. Hackman’s death was the result of significant heart disease, with Alzheimer’s disease as a contributing factor.

Given Hackman’s advanced stages of Alzheimer’s disease, it is “quite possible that he was not aware that she [his wife] was deceased”, Dr Jarrell said.

His autopsy indicated he had not eaten recently, though he showed no signs of dehydration. Officials found no evidence that he had communicated with anyone after his wife’s death and could not determine whether he was able to care for himself.

Ms Piersol said patients with advanced Alzheimer’s aren’t able to pick up on environmental cues like light and darkness, making it harder to determine when he should eat, sleep or bathe themselves.

“Those [cues] are oftentimes just, no longer available to people at this stage of dementia,” she said.

Dr Brendan Kelley, a neurologist who specialises in memory and cognition at UT Southwestern Medical Center, explained why Hackman may also not have been able to call authorities for help. He said Alzheimer’s disease can leave patients caught between emotional discomfort and the inability to act on it.

“A person might feel worried or frightened, but at the same time they might not be capable to take the actions that you or I might normally think to do in order to alleviate that worry or concern, such as calling somebody else, or going to speak to a neighbour.”

Dr Kelley says Alzheimer’s patients experience emotions like pain and sadness, and experience physical needs like hunger and thirst, it’s just harder for them to identify what they are feeling.

He said missing meals could also increase levels of confusion and agitation.

The couple’s deaths and the startling details of Hackman living in the home for a week after his wife’s passing has shocked the Santa Fe area, where the couple had lived for more than 20 years.

“It’s just absolutely devastating,” says Jeffery Gomez, a long-time resident of the city, who remembers seeing Hackman around town in his different cars, always with a smile on his face.

His partner, Linda, said the details were triggering, explaining she cared for her elderly mother with dementia. “Even when you have help, it’s a lot,” she said.

“We know Gene and his wife were very private people and she was probably trying to shield him from the public,” she added, “but the thought of doing that alone? It’s a lot to shoulder.”

Laura N Gitlin, a behavioural scientist who researches ways to support caregivers told the BBC, this is becoming a common problem among caregivers.

“With the aging of a population, we also simultaneously have a shrinking of the number of people in the family, number of children, or relatives who live nearby,” she explained.

Ms Gitlin noted along with there being less caregivers, there is less support for these individuals on making big decisions – such as when it’s time to place a loved one in a home instead of caring for them by yourself.

Jeffery Gomez said he couldn’t understand how no one checked in on the couple for such a long while.

“It breaks my heart he was alone so long.”

A list of organisations in the UK offering support and information with some of the issues in this story is available at BBC Action Line.