If you're sincere, how would you comprehensively describe the background of the shooter and his modus operandi? What sources have you used to gather this information to this point?
[EDIT] FWIW I've yet to see anything that makes me confident enough to assign any strong and specific guess about the guy's motivations. I'm confident in "he was very online" and "he played Helldivers a lot, or at least spent a lot of time communicating with people who do" and that's about all I'd feel comfortable confidently asserting if someone asked me for the "TL;DR" on where we're at on that.