GREENVILLE (AP) — The arrest of an investigator led prosecutors to accept a plea deal in the killing of a mother and daughter in their Simpsonville home nearly two years ago.

Michael Crane, 36, was sentenced to 30 years in prison Monday after pleading guilty to two counts of voluntary manslaughter. He had been charged with two counts of murder in the beating deaths of his girlfriend, Allison Cross, 26, and Cross’ mother, Jane Lanser, 56, in August 2011.

Crane beat the women to death with a hammer after going to buy drugs with his girlfriend, police said.

Officers found the bodies after Lanser failed to show up at work. Crane refused to answer the door, and an officer who entered the home found him in a bedroom, rocking back and forth, with the bodies of the women wrapped in a bloody comforter.

An investigator in the case, Ralph Bobo, was arrested earlier this year after authorities said he tampered with evidence in a different case. Prosecutors considered the death penalty, but decided to accept the plea deal because Bobo would have to testify at trial and his arrest would come out and could influence jurors.

Man gets 30 years for killing two women