LARNED, Kan. (AP) — The Kansas Department of Corrections says an autopsy shows that an inmate convicted of killing two children in 1986 died of unspecified natural causes.

The Topeka Capital-Journal says Nolan Prewett was 66 when he died Jan. 10 at the Larned Correctional Mental Health Facility.

Prewett was serving time for crimes linked to the July 1986 suffocation deaths in Topeka of 3-year-old Shavon Mahomes and her half-sister, 6-year-old Shannon Mahomes. Their bodies were found in a home’s basement.

Prewett was convicted of two counts each of first-degree murder, aggravated kidnapping, aggravated criminal sodomy, rape and enticement of a child.

He received two life sentences to be served simultaneously.