Josef Riegler joined the SS at just 15 and rose to become one of Mauthausen’s most feared guards. Known for brutal beatings, executions, and helping hunt down escapees in the “Mühlviertler rabbit chase,” he left a trail of death and terror. Captured after the war, Riegler confessed to dozens of murders before being hanged in 1947. This is the story of how a young Austrian became a ruthless executioner.