Violent video games desensitize players to real-life violence. It is common for victims in video games to disappear off screen when they are killed or for players to have multiple lives. In a 2005 study, violent video game exposure has been linked to reduced P300 amplitudes in the brain, which is associated with desensitization to violence and increases in aggressive behavior.
I myself am a gamer of... shall we say violent video games. Many of my friends enjoy playing violent video games. all but a few are violent, however, I can assure you that these few friend's violence is not the cause of violent video games. If violent video games caused children to become more violent, and with so many releases of violent games, then why don't we have scores of children fighting and brawling everywhere? I am not sure if you have taken a rather detailed look on the matter but perhaps the children who play these violent video games belong to abusive families and play these video games as a means of escaped from these parents? On that note perhaps these violent video games act as a form of therapy in which the child can take his aggression out on a score of Nazi Zombies or a dozen or so covenant grunts. I know for a fact that I feel pretty calm after calling in a napalm strike in black ops.