Shortly after the start of the Second World War in 1939, the SS murdered thousands of German and Polish psychiatric patients in Poland. At the same time, under the code name of »Reich Committee for the Scientific Registering of Serious Hereditary and Congenital Illnesses«, the murder of more than 5,000 children and adolescents with mental and physical disabilities in the so-called children's wards began in the territory of the Reich and, in 1938, in annexed Austria. Doctors and midwives were supposed to fill in a questionnaire to register the children concerned. Medical experts then selected girls and boys, who were killed by sedatives or starvation.

From 1939 to 1941, institutional patients were the target of the secret »Aktion T4«, organised at Tiergartenstrasse 4: about 70,000 people were murdered by gas in six killing centres. Later, the T4 personnel also murdered about 20,000 concentration camp inmates in the killing centres of Bernburg, Pirna -Sonnenstein and Hartheim .

After the centrally organised »Aktion T4« was halted in August 1941, the killings continued in the hospitals and nursing homes. The group of victims was extended to include old people, those injured by bombs, forced labourers and children in care. Doctors and nursing staff members killed about 90,000 more institutionalised patients through deliberate neglect, starvation and with drugs.