This association has been something that has been studied for years, and until now, not much evidence has confirmed the common association that video games lead to violent behavior. Even after the Columbine incident and other correlations of violence and violent video games, there still has not been true scientific findings on them having a causal relationship until now. I am still not completely convinced that it causes the violence, but it could definitely have an influence. I mean look how much the media influences life everyday, there is no way that people, especially those who spend hours and hours playing these games are not being effected. Even if this is true, there really is no way to completely monitor them or change the industry; they are so integrated into our everyday society.
Here is the link to a summary article about the study : http://www.sciencedaily.com/releases/2013/03/130326121605.htm