Shooter built bombs, was googling stuff about major depressive disorder, didn’t like Trump but wasn’t a big fan of democrats either, seemed to dislike both parties, above average intelligence and probably suicidal.
Hasn’t been a manifesto so far and seems more to be just a suicidal loner situation according to official statements about the guy.
He put a lot of thought into this attack and planning though to have diversion bombs or even worse bombs for taking out crowds of people. Makes me think the civilians hit in the incident aren’t collateral damage at all and he planned to rampage for as long as possible.