There are some big gaps in the news coverage of this story, or maybe I just missed it, but how was he stopped, and arrested? One article said no shots were fired by law enforcement, and it didn't say anything about him being wounded, so how did the arrest take place?
Assuming that he was not wounded, one helpful aspect about all this (if I can put it that way) is that questioning him may provide some useful information. Maybe we could learn what, if any, antidepressant medication he was on, and what violent video games he played. How much of an influence was that horrible web site that he posted his manifesto on? In other words, what can we learn about what makes so many young people go off the rails in this way, over and over again? Many of them are killed themselves, but at least maybe this one can answer some questions.