I was talking more as a generalised type of mass shooter. I do now agree with you that this is probably not this shooter's type, but I still think that what I posted is valid for some of them.
Even the type who act out of hate of humanity due to perceived wrongs against them can keep the feelings in their head and plan a 'great event', I think there can be a lot of differences between the timing of the final 'snap event' and actually committing an atrocity like this, and some may actually never go through with it because something else happens in the interim, in the planning and development stage.
These are my thoughts, anyway. I feel like that mindset has a kind of causality to it that can be 'understood' (I don't mean that it's valid, but just that you can add events together and see how it turned out that way), but this psychopath/sociopath thing is something I have no understanding of....is it even something that can be understood by anyone else? His actions now seem to me to be more of a psychopathic/sociopathic nature.