sentences:  In October 1939 Hitler signed a "euthanasia decree" backdated to 1 September 1939 that authorized "Reichsleiter" Philipp Bouhler, the chief of Hitler's Chancellery, and Karl Brandt, Hitler's personal physician, to carry out a program of involuntary euthanasia.After the war this program came to be known as "Aktion T4", named after Tiergartenstraße 4, the address of a villa in the Berlin borough of Tiergarten, where the various organizations involved were headquartered.T4 was mainly directed at adults, but the euthanasia of children was also carried out.