Police say a South Carolina man died from a heart attack after trying to bury the body of his girlfriend who he had just strangled to death in his backyard.

According to WCHS, deputies with the Edgefield County Coroner’s Office and Edgefield County EMS responded to a call of an unresponsive man laying in his yard.

Joseph Anthony McKinnon, 60, of Trenton, S.C. was found dead next to a freshly dug grave and after digging into the case more, authorities also found the body of 65-year-old Patrica Ruth Dent in the pit, police said according to WCHS.

Police believe that McKinnon attacked Dent in their home, strangled her to death then bound and wrapped her in trash bags before dumping her body in the grave.

Witnesses told police they saw McKinnon digging a hole in his yard the day before the attack happened, reported WCHS.

An autopsy later showed McKinnon died of a heart attack just before he was finished filling in the freshly dug grave.