The Nazi involuntary euthanasia program involved the planned murder of mentally and physically impaired patients and started in September 1939 when the policy was approved by Hitler in a personal decree. He approved the euthanasia of a young disabled boy, Gerhard Kretschmar, at the request of his father, but approval was quickly extended to other disabled children, and then disabled adults. The approval of three doctors was needed for killing of any individual to proceed. The killings were conducted in many hospitals and asylums such as Hadamar Euthanasia Centre by a variety of methods, including enforced starvation, injection of lethal drugs, and gassing using carbon monoxide. Patients were carefully deceived to believe that they were simply taking a shower so as to entice them into the gas chamber, then locked in and asphyxiated through carbon monoxide poisoning. Although public protests led by Bishop Galen and others forced the policy to be officially suspended in 1941, it continued unofficially until the end of the war.