IF VT attempted to intervene prior to this tragedy and in any way impugned the reputation of this student, then VT would have their butts sued off faster than you can say "slander".
Even if VT suspected this guy was a fruitcake, their hands were tied unless and until he made direct threats and the school had reason to believe that he would carry them out. Simply suspecting that this guy was a stalker or that he had a fixation on some girl is not sufficient cause for VT to start sending out warnings to all the other students.
VT was and is in a no-win situation. If they had warned anyone about this guy and they got it wrong, they'd be sued into obvlivion. If they suspected something and didn't warn the student body, then they will be sued.
The way the legal system is set up, nobody is safe from liability or litigation. Damned if you do and damned if you don't. If you don't warn you get sued. If you warn, you get sued. There is no Tarisoff immunity given to educational institutions. If you go around warning students about a suspected nut, you'd better be right and even if you are right, warning is not going to be enough. You will be expected to prevent it.
When they know he's done it to at least 2 girls, he shouldn't have been allowed back on campus.