Why do any of these shooters do it? Usually it is incoherent, and people point

[RockRaven]

to a variety of things about their life as if that explains it.

Often even when they get taken alive like this guy (and it isn't just a rambling manifesto or collection of social media posts left behind) their explanations are a mess in terms of logic, coherence, or reality-basis.

I bet we get a cherry-picked explanation of motive from law enforcement, but that almost certainly won't be the real story in any meaningful way.