(CNN) A Pennsylvania man serving life in prison for the grisly murder of his wife and stepdaughter has confessed to another killing, resolving a cold case from the 1980s, officials said Thursday.

Several other cases are under review, they said.

Regis Brown, 59, admitted to killing Bryce Kenneth Tompkins, 45, whose body was found by hunters partially submerged in Neshannock Creek in Lawrence County in December 1988, authorities said. He told police that Tompkins was killed because he witnessed a burglary.

Brown was sentenced last month in the March deaths of his wife, Michelle Brown, 53, and his stepdaughter, Tammy Greenawalt, 35.

Eric Hackwelder, the attorney who represented Brown during the double homicide case, said he may be retained by Brown to represent him at his October arraignment related to the killing of Tompkins.

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