Posting straight up and summarizing what I've seen so far ...
This 21YO kid seems to have had the not-so-great-all-American upbringing: divorced parents; two houses, no home; father moved on, re-married, re-divorced; probably on ritalin or other psycho-active drugs, moved on to abusing/using other drugs, illegally; maternal uncle tried to mentor but was pushed away by the kid; loner; spent most his time in his room (computer games? Internet?).
My guess is that being nearly fatherless, without a secure home, he sought security and safety in games and Internet discussion/chat (which he could control, to some degree), and in which he found acceptance. Nothing intrinsically wrong with either. And self-medicated with drugs (nothing wrong with medications, properly used and medically supervised).
Guessing further, his rootlessness, fed by the games and (guessing further) the discussion/chat places he hung out mutilated whatever moral ideas he might have had, and they were replaced with racial identity we vs. them thinking. My guess is that if his Internet browsing history can be traced he'll have spent a lot of time on Stormfront-type sites and discussion forums.
