The euthanasia action in Nazi Germany during 1940/41 ("Aktion T4") belongs to the most horrible chapters in history of medicine. The article describes the life of Horst Schumann, who was involved in the murder of more than 15 000 people and after that did cruel sterilization experiments in Auschwitz. It will be depicted the personal characteristics to show, why he was susceptible to this development. The critical look at these events shall warn us not to push away mental patients and mentally handicapped people from our society. The personal rights of this group of patients must not be questioned.