SO is reading a fiction book involving Nazi's and its mentioned that during one of the many street killings of Jews, one soldier collapses and another refuses to kill anymore..another mentions a soldier getting up in the middle of the night and walking out their station and killing themselves..
Is there any proof things like this occurred, or if there was a refusal to kill, what would be their punishment ?
I don't know about breakdowns, but the psychological toll it exacted was noted. Himmler gave a speech to a group of SS men on Poznan, where he discussed the difficulty of performing mass killing:
I also want to mention a very difficult subject before you here, completely openly. It should be discussed amongst us, and yet, nevertheless, we will never speak about it in public.
I am talking about the "Jewish evacuation": the extermination of the Jewish people. It is one of those things that is easily said. "The Jewish people is being exterminated," every Party member will tell you, "perfectly clear, it's part of our plans, we're eliminating the Jews, exterminating them, ha!, a small matter."
And none of them has seen it, has endured it. Most of you will know what it means when 100 bodies lie together, when there are 500, or when there are 1000. And to have seen this through, and -- with the exception of human weaknesses -- to have remained decent, has made us hard and is a page of glory never mentioned and never to be mentioned.
Additionally, the decision to switch from mass shootings to gassings was apparently made due to concerns for the killers--apparently a number of them suffered from mental problems after, and Himmler, after witnessing such a killing, pushed for switching to gas. Wikipedia cites Richard Rhodes' Masters of Death, a book about the Einsatzgruppen--unfortunately I don't have it on hand, so I can't cite it myself.