German authorities have rejected a former Auschwitz death camp guard's bid for clemency, removing the final barrier to the 96-year-old serving his sentence for accessory to murder. Prosecutors rejected former SS sergeant Oskar Groening's clemency request filed earlier this week, per the AP. Groening had been known as the "bookkeeper of Auschwitz" because he reportedly was responsible for gathering the cash of new camp arrivals and sending it to Berlin, reports CNN. Groening was convicted in 2015 and sentenced to four years in prison, though he has remained free while he appealed. He's expected to begin his sentence soon. (More Auschwitz stories.)