Oxford University staffer Andrew Warren pleaded guilty in a bizarre “sex fantasy” murder of a former Northwestern University professor’s boyfriend, The Chicago Tribune reports. As part of his plea deal, the 58-year-old agreed to testify against former professor Wyndham Lathem—who is accused of stabbing his boyfriend repeatedly while Warren filmed the incident. In exchange for his testimony, prosecutors will reportedly recommend that Warren be sentenced to 45 years in prison. No trial date has been set for 44-year-old Lathem, who pleaded not guilty to the killing.

According to prosecutors, Warren and Lathem chatted for months online about their sexual fantasies of killing people. Lathem then allegedly flew Warren out to Chicago in 2017 to bring their fantasies to life. Lathem’s boyfriend, 26-year-old Trenton Cornell-Duranleau, was allegedly stabbed repeatedly by Lathem while he slept. Warren and Lathem then fled Chicago after the murder, but were eventually caught in California.