Who was it? Jordan Peterson the clinical psychologist I think, said something about how people who can't find a way out of their situation, or perhaps were never given the values or tools to do so, become bitter and sad, and then hateful, and then vengeful. The people at rock bottom. Things are done for them. They have nothing to build upon, only the short stint of self destructive highs that permeate their existence, so they are going to take everyone else down with them. They are going to take vengeance for the fact they exist. I would say that psychologically, many of the people involved in this probably fit that psychological profile.