Heinrich Himmler visited the outskirts of Minsk in 1941 to witness a mass shooting. He was told by the commanding officer there that the shootings were proving psychologically damaging to those being asked to pull the triggers. Thus Himmler knew another method of mass killing was required. After the war, the diary of the Auschwitz Commandant, Rudolf Höss, revealed that psychologically "unable to endure wading through blood any longer", many "Einsatzkommandos" – the killers – either went mad or killed themselves.