I realize this is not addressing the categorization question, but ...there were many mass burials all over Europe, unfortunately, during the Holocaust. There are many instances of the Nazis occupying towns, one by one, as they took control of countries. Their standard process was to gather all Jews in one place, march the able bodied men out of town to the nearest forest, have them dig a huge ditch, then force them into it and shoot them all. The next day they would bring the rest of the Jewish population there, have them climb in on top of the men and shoot them. They did this in several different countries they occupied, but perhaps most notable is Lithuania, where in a period of two months they eliminated 93% of the Jewish population of the country, systematically, in about 150-200 different towns as they advanced.