Action T4: A Doctor Under Nazism

Between 1939 and 1945, at least 200,000 people with disabilities were assassinated by the Nazi regime by the Action T4 plan. Dr. Julius Hallervorden, a major brain pathologist, contributed to the systematic murder and recovered the brains of 690 victims. After the war, he still pursued a brilliant career, in all impunity, and died covered in honors. How?