Destructoid has an excellent recap of a CNN Town Hall lead by Anderson Cooper that actually discusses the issue of gun violence in a sensible way (thanks to PHX Corp. for the link in the shout box) and even includes a lengthy discussion on mental health issues. The segment highlighted by Destructoid from CNN's Town Hall: Guns Under Fire special called "The mental health stigma and violence" features Grand Theft Childhood author Cheryl K. Olson, who has proven to be a reasonable voice in just about every public forum I have seen her speak on.
While the segment is not all that long, Olson points out that, according to her own research, "[T]he typical 13-year-old boy is playing at least one mature-rated violent game on a regular basis. And when you are looking at something very rare like a school shooting, and something that's statistically normal like playing violent videogames, it's kind of hard to make that link."
Host Anderson Cooper agrees with her, noting: "I looked at the study in ten different countries between gun violence and videogame sales, and it doesn't seem like there's a link in all these different countries."