Francis Dresser of Douglas County died from injuries suffered when she was shot once in the chest Sunday while at Carson-Tahoe Regional Medical Center, Carson City Sheriff Ken Furlong said.
Her husband told officers he planned to "end his wife's suffering" by killing her and then himself, but his gun jammed, police said.
District Attorney Neil Rombardo said William Dresser, 88, was charged Wednesday with "open murder" with use of a deadly weapon.
Rombardo said open murder gives him discretion to amend the charges as more facts about the case emerge. Nevada law does not recognize or make a distinction for so-called mercy killings, he said.
"Filing open murder allows us to achieve justice for the victim, for the family and the community, which is our ultimate goal," Rombardo said.
William Dresser was scheduled for an initial court appearance Thursday.
He was arrested Sunday after firing one shot at his wife with a small-caliber handgun.
The shooting happened on the third floor in the hospital's rehabilitation ward, where Francis Dresser was being treated for a previous injury.
"Dresser suggested to officers that his motive was to end his wife's suffering," Furlong said.
"My heart goes out to the family," he said.
According to a police report, William Dresser told officers he had brought four bullets - two for his wife, two for himself - but the gun jammed after the first shot.
State Department of Corrections officers who were nearby and hospital security subdued William Dresser until deputies arrived.
The man was "crying and mumbled words to the effect of, 'I did not accomplish my goal,'" an officer wrote.
After the shooting, Francis Dresser was flown to Renown Regional Medical Center in Reno, where she died three days later.
Authorities were investigating William Dresser's claims that his wife became paralyzed and incapacitated after a fall at the couple's home two weeks ago. The couple had been married 63 years.
William Dresser remained at the Carson City jail and was on suicide watch, Furlong said.
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