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._](/actionline/)