How did it go on for two hours when the guy walked all the way across campus?
They put the school on lockdown for a while and then lifted it under the impression that it was an isolated incident and the students would be safer in class.
The informed news is that the guy found his ex-girlfriend in bed with a guy and killed them both, which set him off, but I'm doubtful whether that will turn out to have been the case.
The news seems to have a lot of theories, but most of it is based on rumors they've heard from students. Everything seems to point o some sort of domestic dispute possibly being the trigger, though. I think the popular word now is that the guy went to the dorm looking for his girlfriend and instead got into some sort of dispute with her roommate and one of the RA's and then later went to look for her in the academic building. Until there is official word, though, there's no telling what the truth is.
Theres always gonna be ways to get an gun, especially on the black market.
You really overestimate the accessibility of the black market. It's not like logging into blackmarket.com and ordering for home delivery. Most average Americans wouldn't even know where to begin looking for an illegal firearm. What's more, in situations like this, you also have to take into account the area. Blacksburg isn't exactly a major metropolitan area. Virginia Tech takes up half the town. I can't imaging the criminal underground is a major element out in the middle of nowhere in Virginia.