Okay, first of all, there's no need to go all kwyjibo just because there may be something to what this profiler is saying. One of the attractive things about D&D in particular is that you're not just role-playing, but you're role-playing heroes, often very powerful ones. This is her (his?) point. This sniper seems to get off on being such a dangerous, bad-ass, I'm-sick-of-it-all-and-I'm-going-to-do-whatever-the-frag-I-want kind of guy. And before he snapped, he probably fulfilled those fantasies in other, more harmless and common ways, like watching "guy" movies and maybe even playing D&D. I'm surprised she didn't mention video games explicitly.
The real shame is that her mention of super-heroes and D&D are likely to conjure for people an image that she may not have intended.