During their work in the quarries, the prisoners were abused, beaten to death, shot, and »sprayed,« i.e., killed by injections in the camp’s sick ward. They were killed in winter during so-called »bathing actions« or they died from malnutrition and exhaustion. Mainly affected by these extermination measures were Jews of all national backgrounds, Poles, Soviet POWs, »Gypsies,« and Spanish Republicans as well as prisoners, who had been sent to »safety custody« and had been openly slated for »extermination by labor.«

In the euthanasia-facility in Hartheim near Linz, sick and weak prisoners were killed in 1941/42 and in 1944.

Mauthausen gas chamber construction was started in the fall of 1941 in the crematory area. From a room adjacent to the actual gas chamber, a container that was especially constructed for this purpose was filled with cyclone B, from where the gas was fed into the gas chamber through a fan and a pipe. According to statements of the court of law in the city of Hagen and recent research, it can be assumed that at least 3455 persons, most of them Soviet POWs, were killed in the gas chamber of Mauthausen. In fall 1941 – or in spring 1942 according to other sources – the SS began to use a gas truck, in which at least 900 prisoners were killed. In the last days of April and the first days of May 1945 the SS ordered the technical equipment of the gas chamber to be dismantled and all incriminating documents to be burned.