While they have become increasingly more frequent, these incidents remain anomalies with the killers reaching extremes that appear to be totally unpredictable IMO. All the warning signs are possessed by large numbers of people who do not reach this point. I do think it is a perfect storm of circumstance and mental state, combined with awareness of the possibility due to media coverage. Most police are not trained to handle it - it is so rare that only specialized teams at higher up levels are going to be truly trained for anything similar. And "people with mental health problems" is not a category with any meaning and by its nature never will be. Right now you have pretty much have felons, people who have been declared incompetent or had some other sort of extreme mental health adjudication (very rare), and everyone else. Background checks generally determine where someone falls. The first two cannot buy guns. The last group can without much restriction. This is one issue where I believe there virtually no in-the-middle meaningful solutions - background checks, home visits, etc. There aren't really even extreme solutions. There are no reliable variables to judge who does this - every one that is focused on, even if it has a clear connection, applies to such a huge group of people that is so poorly defined that attempting to control it would likely make things worse. Very upsetting situation, and the debates just make me feel worse because they all make people angrier without having any real hope of a solution. Depressing.
You did a good job conveying reasons someone might open carry an assault weapon. But the reasons seem so far out there that they sound like "satire" to me. Maybe that would have been a better word. I just have a hard time wrapping my mind around that kind of thinking. The killer's mother philosophically and materially aided and abetted her son to commit these murders (although not in the legal sense of the term) IMO.