A man who was convicted of first-degree murder in the 1994 death of a Johnston woman killed himself Friday.

Jerry Lee Proctor hanged himself at the Anamosa State Penitentiary, officials said. The cause of death is believed to be asphyxiation, pending an autopsy. According to a release, Proctor was taken by ambulance to the Jones Regional Medical Center, where he was pronounced dead at 5:15 p.m. Friday.

Proctor was serving a life sentence for the murder of 38-year-old Patricia Howlett. Howlett’s throat had been slit, and she had been raped and beaten before being set on fire near a Des Moines ballpark. Proctor was arrested over a year later and began his life sentence February 14, 1997.