"The top of the top." Clearly Holmes is brilliant. So this is a "what happened" mystery. Whatever it is, it didn't seem to happen in a "snap" moment. And if it did, that moment came several months ago and he had the discipline to plan this over that period of time. And the point about no social media footprint is interesting.
What also sets this shooting apart from almost all other is the lengths to which he went to make sure he survived it; body armor literally from head to toe. In a line most often attributed to Winston Churchill: ..."an enigma, wrapped in a riddle, surrounded by mystery."