The mysterious deaths of Oscar-winning actor Gene Hackman and his pianist wife, Betsy Arakawa, continue to keep stumping authorities amid their investigation. 

Earlier this week, the Santa Fe County Sheriff’s Office confirmed that there were ‘no significant findings’ of gas leaks or carbon monoxide at the couple’s home in Santa Fe, New Mexico, where they were found ᴅᴇᴀᴅ during a welfare check on February 26.

At this time, authorities have stated that it is still unknown how they died and that their remains were partially mummified, indicating they had been ᴅᴇᴀᴅ for several days. 

‘Initially I was thinking carbon monoxide,’ Chief Medical Examiner James Gill, who is not investigating Hackman’s death, said. ‘You’re thinking of something that all the people would be exposed to. But the fact that that’s negative then you start wondering about not only the cause of death, but the manner of death.’

Gill proceeded to theorize that Hackman may have collapsed since he has ‘a history of heart disease.’ 

‘He’s got a pacemaker. So that would not be unusual. But the unusual part is that why then did she also collapse,’ Gill noted to People.

The mysterious deaths of Oscar-winning actor Gene Hackman and his pianist wife, Betsy Arakawa, continue to keep stumping authorities amid their investigation (pictured in 1991)

Gill, then, pointed out: ‘If she had found him alive, why didn’t she call 911? Which, you know, usually that’s a person’s first instinct.’ 

‘Maybe they had agreed that if he was found, he didn’t want to be resuscitated. She may have panicked and then either had a primary heart event herself, a cardiac event or maybe she got despondent, and she took pills,’ he speculated. 

Read More Gene Hackman police blunders leads to series of troubling unanswered questions

Gill detailed that the next steps for the medical examiner are ruling out any injuries from falling and analyzing the ‘toxicology and autopsy results’ to exclude a drug-induced death. 

‘I think the autopsy and the toxicology testing are really going to be what’s needed in order to make that final determination,’ he explained. ‘Otherwise, it’s kind of speculation at this point.’

Gill went on to share another possible theory that involved Arakawa unexpectedly dying first and Hackman collapsing ‘from the stress’ of trying to ‘get help.’

‘He’s older, he’s got known heart disease. But the autopsy would certainly show if she had heart disease or cancer or what have you,’ Gill said.

Arakawa’s body was found in a bathroom near unidentified pills strewn from a prescription bottle, while Hackman’s remains were found in the home’s entryway. Hackman’s glᴀsses and cane were on the floor beside him, suggesting he had fallen just before his death. 

It is still unclear who died first – Hackman or Arakawa. But fire chief Brian Moya said the location of their remains suggests it was around the same time. 

Earlier this week, the Santa Fe County Sheriff’s Office confirmed that there were ‘no significant findings’ of gas leaks or carbon monoxide at the couple’s home in Santa Fe, New Mexico , where they were found ᴅᴇᴀᴅ during a welfare check on February 26; seen in 2003

‘Initially I was thinking carbon monoxide,’ Chief Medical Examiner James Gill, who is not investigating Hackman’s death, said. ‘You’re thinking of something that all the people would be exposed to. But the fact that that’s negative then you start wondering about not only the cause of death, but the manner of death’ (pictured in 2003)

‘Just because both bodies were in similar ways where we, as experts, sad to say that we know a lot about how people die and how long people are ᴅᴇᴀᴅ for – both bodies are in a similar manner that it could be a similar timeframe,’ Moya told Fox News.

Moya didn’t say whether ‘similar timeframe’ could allow to Arakawa to find Hackman ᴅᴇᴀᴅ and kill herself in despair, or for the couple to carry out a suicide pact which could have seen Arakawa help her frail husband to die before taking her own life.

Moya noted the couple’s property spanned more than 9,000 square feet across three structures, so it’s telling that both bodies and that of their dog Zinna, were found in the same building.

The couple’s German shepherd, named Bear, survived along with a second dog named Nikita, according to Joey Padilla, owner of the Santa Fe Tails pet care, where Hackman and Arakawa often boarded their dogs. Both are being cared for.

Hackman and Arakawa likely were ᴅᴇᴀᴅ for nine days until their discovery on February 28.

Hackman was among the finest actors of his generation, appearing as villains, heroes and antiheroes in dozens of dramas, comedies and action films from the 1960s until his retirement in the early 2000s (seen in 1993)

One of the surviving dogs was found near Arakawa’s body and the other outside the couple’s home.

Zinna, the dog that died ‘was always attached to Betsy at the hip and it was a beautiful relationship,’ Padilla told the ᴀssociated Press.

‘Zinna went from being a returned shelter dog to this incredible companion under Betsy’s hand.’

The mystery of the couple’s deaths has only deepened as police said they have found no evidence of carbon monoxide poisoning.

The two bodies both have tested negative for carbon monoxide, and no gas leaks were discovered in or around the home.

Santa Fe County Sheriff’s Office said there were no signs of foul play or external trauma on the couple’s bodies.

Sheriff Adan Mendoza added that he could not completely rule foul play out while the investigation continues.

The deaths were originally deemed suspicious enough to warrant a full investigation but cops no longer believe anyone else was involved.

Hackman’s pacemaker last recorded him alive on February 17 – nine days before his body was found.

At this time, authorities (seen last month at a press conference) have stated that it looks like the pair had been ᴅᴇᴀᴅ for days and it still remains unclear how they died

Police do not suspect foul play, despite the front door being found ‘ajar.’ There were no signs of forced entry into the home.

‘I think I’m pretty confident that there is no foul play just based on the lack of evidence,’ Mendoza later told Today. ‘But, of course, we’re not ruling that out.’

The case is shrouded in the kind of intrigue reserved for Hackman’s detective thriller novels and has garnered international attention – with many wondering how their deaths went unnoticed for so long.

Neighbors in their gated private community off a winding canyon road five miles outside of Santa Fe told The New York Times that despite living with the celebrity couple for years, most of them never even caught a glimpse of them.

Earlier this week, Gill revealed putting a time on death becomes increasingly difficult once a body has undergone significant decomposition, especially when mummification occurs.

‘Once you get to that mummification stage, there’s nothing to be able to distinguish the two deaths timewise,’ he told People. 

Hackman met Arakawa, a classically trained pianist who grew up in Hawaii, when she was working part-time at a California gym in the mid-1980s; pictured in 1991

The expert added environmental factors such as dryness and heat can accelerate decomposition, making it harder to pinpoint the cause and time of death.

He said: ‘Generally, dry environments will cause mummification to occur more quickly than in a non-dry environment.’

Forensic pathologist Judy Melinek, who also spoke to People, added it’s very difficult to determine time of death once decomposition has set in.

She said: ‘Once the body is decomposed, it’s a lot harder to do.’

The expert added early indicators including rigor mortis and body temperature help in the initial stages of putting a time on death, but are unreliable once decomposition progresses.

He was a five-time Oscar nominee who won for The French Connection in 1972 and Unforgiven two decades later; seen in 1996

Hackman, a two-time Oscar winner with an estimated net worth of $80 million, just turned 95 in late January. He became a recluse in the last 20 years of his life, after retiring from acting in 2004.

He moved to New Mexico shortly after making a movie there in the 1980s and loved the quiet pace of life and the fact locals left him in peace.

Hackman was among the finest actors of his generation, appearing as villains, heroes and antiheroes in dozens of dramas, comedies and action films from the 1960s until his retirement in the early 2000s.

He was a five-time Oscar nominee who won for The French Connection in 1972 and Unforgiven two decades later. 

Hackman met Arakawa, a classically trained pianist who grew up in Hawaii, when she was working part-time at a California gym in the mid-1980s, the New York Times reported in 1989. They soon moved in together, and by the end of the decade had decamped to Santa Fe.