Authorities in Oklahoma have charged the man who beheaded a coworker at a food processing plant with first-degree murder.

The Associated Press reports that the charges come nearly a week after 30-year-old Alton Nolen brutally murdered Colleen Hufford, 54, at the Vaughan Foods plant in Moore, Okla. Nolen, who had just been fired, proceeded to attack 43-year-old Traci Johnson until he was shot by company CEO and Oklahoma County reserve deputy Mark Vaughan.

According to the Associated Press, Nolen converted to Islam shortly before the attack. The FBI began probing his background, though no link to terrorism has been established at this time.