ALPENA, Mich. (AP) — One of two northern Michigan men charged in the deaths of two women pleaded guilty to reduced charges Thursday and has agreed to cooperate in the prosecution of his co-defendant, prosecutors said.

Joshua Wirgau, 35, of Alpena, pleaded guilty to one count each of involuntary manslaughter and disinterment and mutilation of a dead body, accessory after the fact, prosecutors said.

A sentencing agreement requests 15-30 years in prison, prosecutors said.

Wirgau agreed to cooperate in the case against Brad Srebnik, 37, who’s charged with five crimes, including first-degree murder in the deaths of Brynn Bills, 17, and Abby Hill, 31, both of Alpena.

It wasn’t clear whether Srebnick had entered a plea in the case or has an attorney who might comment on the allegations against him. Court records for the case weren’t available online and Nessel did not address those questions in her news release.

Bills was last seen in August 2021. Her body was unearthed the next month in Wirgau’s yard in Alpena Township, according to prosecutors.

Hill, 34, was found dead in a wooded area in the township. She was aware of what happened to Bills and was killed to keep her quiet, Nessel’s office has said.

Prosecutors haven’t revealed a motive for Bills’ death.