Over at Concurring Opinions, my colleage Don Braman has a post that begins:

  We've all been flooded with information about the horrible shootings at Virginia Tech. Perhaps you've heard from friends or politically minded bloggers about what this means about guns and gun control. As part of a team of researchers that studies the way people process information about firearms and their regulation, I can tell you that this is a natural way to react to tragedy.
  But if you look at public opinion following each major school shooting over the last twenty years, can you guess which way the shootings have driven public opinion on gun control? Neither way. That's right, each school shooting has had exactly no effect on public opinion regarding gun control.