This is while the other two dogs owned by the celebrity couple were found to still be alive, despite their owners having died up to two weeks before their bodies were discovered.
Hackman, a two-time Best Actor winner at the Oscars in 1971 and 1992, and classical pianist Arakawa were found deceased at their home in Santa Fe, New Mexico on 26 February. This was alongside their dog, Zinna.
Mystery initially surrounded their death, with it being treated as 'suspicious' for a full investigation to take place, given that both bodies were found separate in the house and partially mummified.
After investigating the home and conducting post mortem examinations, doctors ruled that Arakawa had died from a rare disease known as hantavirus pulmonary syndrome; a flu-like infection that is transmitted from the faeces of rats.
Her body was found in an upstairs bathroom of their home.
She is believed to have died on or around 11 February. Tragically, with 95-year-old Hackman living with severe Alzheimer's, officers believe he didn't understand what had happened.
Around a week later on 18 February, Hackman himself passed away downstairs in the home's mudroom after his pacemaker noted an abnormal rhythm.
He had been living with severe heart disease and kidney disease, with his autopsy showing no food in his stomach at the time of his death.
Hackman and Arakawa in 1986 (Donaldson Collection/Michael Ochs Archives/Getty Images)
Alongside the couple, one of their three dogs, a 12-year-old Australian Kelpie mix called Zinna, was found deceased in the same bathroom that Arakawa was found dead.
Zinna had been placed in a crate that was locked before Arakawa died, with the dog recovering from surgery. She had picked it up from the vet the morning of 9 February.
And while police are still waiting for autopsy results for the dog, New Mexico State Public Health Veterinarian, Erin Phipps, has revealed that dehydration and starvation are two likely causes of death.
The couple had been together for decades (Kevin Winter/Getty Images)
With dogs unlikely to get ill from hantavirus, Phipps said Zinna being locked in the cage is likely to have caused her to pass away. Her stomach was empty.
The other two dogs owned by the couple, a German Shepherd named Bear, and a second dog named Nikita, were found alive and well on the couple's 12-acre property.
The home had a dog door meaning they could come and go as they pleased, accessing food and water that will have kept them alive.
For now, the case looking in to the deaths of Hackman and Arakawa will remain open for officials to 'close the loopholes' in the case, such as the how Zinna died.
Hackman was 95 when he died (Vera Anderson/WireImage)
Santa Fe Sheriff, Adam Mendoza, said they are still waiting on phone records even though they believe it is 'very unlikely' anything new will be found.
He said: "I don't know if he used cell phones or technology or emails, there's no indication of that. So right now, there is no activity from Mr. Hackman."
