SANTA FE, N.M. (AP) — Actor Gene Hackman died of heart disease a full week after his wife died from hantavirus in their New Mexico home, likely unaware that she was dead because he was in the advanced stages of Alzheimer’s disease, authorities revealed Friday.

Hackman, 95, and Betsy Arakawa, 65, were found dead Feb. 26. In the days that followed, mystery swirled around the deaths as authorities ruled out foul play, and immediate tests for carbon monoxide poisoning were negative.

Then authorities in New Mexico released the causes, proposing a simple but tragic theory for the deaths: Shortly after Arakawa’s death from a rare infection, Hackman died of the nation’s leading killer — heart disease — apparently unable to seek help after his wife died.

“I believe they really discovered what truly happened in this case,” said forensic pathologist Dr. Victor Weedn, who was not involved in the investigation. “It seemed such a great mystery to the entire nation.”

Here’s a timeline of events surrounding the couple’s deaths:

Feb. 11

Arakawa’s last known activities happened this day. She emailed with a massage therapist in the late morning, visited a grocery store in Santa Fe in the afternoon, then went to a pharmacy and a pet food store, Santa Fe County Sheriff Adan Mendoza said.

At 5:15 p.m., Arakawa entered the gated community to the home she shared with Hackman. Mendoza said investigators found no other communication or activity by Arakawa after Feb. 11, which they believe to be the day of her death. The medical examiner said she may have been experiencing symptoms of hantavirus before her death.

Feb. 17-18

Hackman’s initial pacemaker data revealed cardiac activity Feb. 17. Subsequent pacemaker investigation showed an abnormal rhythm of atrial fibrillation Feb. 18, the last record of heart activity.

Based on this information, chief medical examiner Dr. Heather Jarrell said it is reasonable to conclude that Hackman probably died around Feb. 18.

Feb. 26

A maintenance worker who showed up to do routine work at the house could not get inside and called a security worker, who spotted two people on the ground inside the home, Mendoza said. The worker called 911 and told an operator he did not know if they were breathing. He and another worker later told authorities that they rarely saw the homeowners and that their last contact with them had been about two weeks prior.

Police found Hackman in an entryway and Arakawa in a bathroom, as well as a deceased dog in a closet.

Arakawa had picked up the kelpie mix named Zinna from Gruda Veterinary Hospital on Feb. 9 after a procedure was done, according to the sheriff. He said the hospital visit might help explain why the dog was found dead. A necropsy is being done on Zinna to determine the cause of death, he said.

Two healthy dogs were found on the property — one inside and one outside.

Feb. 27

Autopsies were done on Hackman and Arakawa. Detectives wrote in a search warrant that the couple and the dog had been dead for some time when the maintenance worker discovered their bodies.

Feb. 28

Preliminary autopsy results didn’t reveal causes of death but showed Hackman and Arakawa were not killed by carbon monoxide poisoning, the sheriff said. The initial autopsies also found no external trauma to either body.

March 7

Authorities reveal causes of death for Hackman and Arakawa. Jarrell said both deaths were from natural causes.

Hackman’s death was tied to heart disease with Alzheimer’s disease contributing. Authorities linked Betsy Arakawa’s death to hantavirus pulmonary syndrome, a rare but potentially fatal disease spread by infected rodent droppings.