Tennessee officials say a 54-year-old Death Row inmate convicted in the 1987 murders of a Memphis convenience store clerk and a policeman in Oklahoma died today of natural causes.

According to the Department of Correction, Michael Wayne Howell was pronounced dead of natural causes this morning at the Lois M. DeBerry Special Needs Facility in Nashville.

Howell was convicted of first degree murder and grand larceny in Shelby County, according to the department. He was sentenced to death on Oct. 26, 1989, for the 1987 murder of Alvin Kennedy, a Memphis convenience store clerk.

Howell was also convicted of first degree murder and sentenced to death in Oklahoma for the Nov. 2, 1987, shooting death of Sgt. Charlene Calhoun.