The type of kid who is disengaged from his family - particularly from his father - seems to be the type who is really attracted by Islam and jihadist fantasies. When you look at the other young Americans who have been involved in this stuff, Hinrichs' fits the profile perfectly. Plus, it's obvious that his family would have had no idea what he was doing, since his communication seems to have been an occasional e-mail and this 1/2 visit.
This could still be simply some depressed loner, and the supposed jihadist material allegedly found (and reported by a source of unknown credibility) might just be stuff he downloaded while searching for recipes and instructions on making explosives and a suicide vest. I gather such "recipes" are a common feature of jihadist websites.
BTTT