The Nazis decided that it was a waste of time and money to support the handicapped. During Hitler's "cleansing program", thousands of people with various disabilities were deemed useless and simply put to death like dogs and cats.
"In the postwar world, Auschwitz has come to symbolize genocide in the twentieth century. But Auschwitz was only the last, most perfect Nazi killing center. The entire killing enterprise had started in January 1940 with the murder of the most helpless human beings, institutionalized handicapped patients..." Henry Friedlander, The Origins of Nazi Genocide: From Euthanasia to the Final Solution
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"Reichsleader Bouhler and Dr. Brandt M.D. are charged with the responsibility of enlarging the authority of certain physicians to be designated by name in such a manner that persons who according to human judgement can upon most careful diagnosis of their condition of sickness be accorded a mercy death.
Signed - A. Hitler".
From the form letter sent to relatives of the victims:
"In view of the nature of his serious, incurable ailment, his death, which saved him from a life long institutional sojourn, is to be regarded merely as a release."
Cordially,