FORT WAYNE, Ind. (WOWO): A 23-year-old man already serving time for a clothing store robbery pleaded guilty Thursday to murder.

Xavier Miller is already serving 12 years behind bars for robbing a store on the south side of Fort Wayne, but while there, decided to tell police he was also responsible for the murder of 19-year-old Porter Billians, which happened just two days before the robbery.

He told police he lured Billians to an abandoned house on Kent Road in September 2015, pulled out a handgun and shot him in the head, then stole his money and phone.

The Journal Gazette reports that Miller confessed because he couldn’t sleep and wanted to make peace with himself. He could get 50 additional years in prison when he’s sentenced in January.