@auschwitzmuseum I recall Tadeusz Borowski in (as it's called in English) "This Way for the Gas, Ladies and Gentlemen" about his time as an (unofficial?) kapo in Auschwitz, at some point they stopped gassing Aryan[ish]* Poles who did as they were told, which in his case involved the ad hoc murder of prisoners almost at random…which contributed to his suicide after the war.
*Nazis believed there were lost Aryans among the Poles, going so far as to kidnap some Polish children to Germans to raise.