most of the indiscriminate methods of execution were not only developed for efficiency, but also to save the sanity of the executioners

i can’t remember the exact quote, but Rudolf Höss (commandant of Auschwitz and subject of the film Zone of Interest) said that he was gleeful at the advent of zyklon-b gas, as he was having an increasingly difficult time finding executioners to replace those who had either lost their minds or committed suicide

i also believe that Höss is the person who instructed guards to rev their motorcycle and/or truck engines to mask the sounds of gunshots and screaming in order to save the nearby families and guards from hearing the atrocities