Besides issuing certificates with fake causes of death, numbered and dated to conceal the group nature of the operation, Wirth’s registry sent out letters of condolence to next of kin citing the fictional cause of death. Himmler was deeply involved since the SS administered both the crematorium orderlies and the camouflage ambulance service, the Public Welfare Transport for the Sick Company, which brought the patients from the institutions to the killing centers.

Peter Padfield, author of Himmler, 1990