I believe I saw this in one of historian Sir Martin Gilbert's books but I have not seen it elsewhere nor do I know which book of Gilbert's it was. Note that I am not talking about SS but what I recall is that it was regular German army. Maybe it was only non-nazis among the army observing a brutal attack by civilians and not only not participating but even saying, Hey, maybe you want to tone it down? Does anyone have any information on this?
EDIT: The title should be "is there any evidence..." because I am really wondering whether it happened or not. It is not possible that it happened if we know that it did not in fact happen. Gilbert mentions it having happened and I am looking for more information on this.