EDDYVILLE, Ky. (WMDJ) — A Kentucky death row inmate who was sentenced in Floyd County has died in prison exactly 29 years after receiving his death sentence.

Donald Johnson, 59, died Oct. 1 at the Kentucky State Penitentiary in Eddyville, according to reporting by the Lexington Herald-Leader. The Kentucky Department of Corrections said his death does not appear to involve criminal activity. An autopsy is pending.

Johnson was sentenced to death in Floyd Circuit Court on Oct. 1, 1997, for the 1989 killing of 61-year-old Helen Madden, who worked at the Bright ’N Clean Laundry in Hazard.

Court records show Madden was working near closing time when Johnson entered the business and asked to use the telephone. After Madden eventually told him he needed to leave, Johnson attacked her, sexually assaulted her and stabbed her more than two dozen times. He also stole about $270 from the business. Johnson was arrested two days later.

Johnson later pleaded guilty to murder, first-degree robbery, first-degree burglary and two counts of first-degree sexual abuse.

In the Oct. 1, 1997 edition of The Floyd County Times, it was reported that Floyd Circuit Judge John David Caudill imposed the death sentence after a penalty-phase trial. The newspaper also reported that Johnson's defense presented evidence concerning his abusive childhood and mental health, but Caudill determined those circumstances did not outweigh the crime.

Johnson spent decades challenging his conviction and sentence in state and federal courts. The Sixth Circuit Court of Appeals rejected his latest federal appeal in January.