Inmate Raymond Shuman, who has been behind bars since 1958, died at Carson Tahoe Medical Center in Carson City around 2:25 p.m. Friday.
Shuman has been housed at Northern Nevada Correctional Center before he was taken to the hospital. He was 83 years old.
The Nevada Department of Corrections says that Shuman was serving two life sentences for first-degree murder.
An autopsy will be scheduled to determine the cause of death. Next of kin have been notified.