Gene Hackman death: Alzheimer's impact on actor in days after wife's death

Hackman likely survived alone in the home for about a week, until he died around Feb. 18, which was the last time activity was recorded on his pacemaker.

Leading up to their mysterious deaths, the actor's wife appeared to be the primary caretaker of Hackman, according to Dr. Baden. 

Chief Medical Investigator Dr. Heather Jarrell performed a full autopsy on Hackman the day after his body was discovered, which showed "severe heart disease, including multiple surgical procedures involving the heart, evidence of prior heart attacks, and severe changes of the kidneys due to chronic high blood pressure."

She added, "Examination of the brain showed advanced Alzheimer's disease as well as blood vessel changes in the brain secondary to chronic high blood pressure."

Jarrell noted that Hackman's pacemaker data indicated an "abnormal rhythm of atrial fibrillation" on Feb. 18. She said it was "reasonable to conclude" Arakawa died the week before Hackman, with the actor's death likely on Feb. 18.

WATCH: NEW MEXICO OFFICIALS CONFIRMED GENE HACKMAN AND HIS WIFE BETSY'S CAUSE OF DEATHS

Fox News Digital medical contributor, Dr. Marc Siegel added that if Hackman's Alzheimer's was "severe," he wouldn't have realized his wife was dead. 

"If he was incapable of calling 911, and getting her seen, and just sat there for a week, then he either went into a state of great despondency or was somehow incapacitated himself," Dr. Siegel remarked. "Or his Alzheimer's was so severe that he was incapable of even noticing what was going on."

Meanwhile, when asked if authorities believed Hackman was able to live on his own and survive after his wife died, Chief Medical Investigator Dr. Jarrell noted that the Oscar-winning actor was in "a very poor state of health."

"Mr. Hackman showed evidence of advanced Alzheimer's disease," Jarrell said. "I'm not aware of what his normal daily functioning capability was. He was in a very poor state of health, and he had significant heart disease. And I think ultimately that is what resulted in his death."

LISTEN: GENE HACKMAN 911 CALL

Officials confirmed that no external trauma was seen on either Hackman or Arakawa, and New Mexico authorities promptly launched a criminal investigation into their deaths.

Hackman and Arakawa previously tested negative for carbon monoxide, Sheriff Adan Mendoza confirmed last week. Their residence was tested for the colorless, odorless gas and was cleared by the Santa Fe City Fire Department after authorities were unable to find evidence of a carbon monoxide leak or poisoning.

Fox News Digital's Tracy Wright and Ashley Papa contributed to this report.