People use what information they have. If the only information you have about going on a killing spree is from a violent video game and you want to go on a killing spree, then you are probably going to use that game for reference unless you do months of other research. Also, if someone is truly angry enough to do something as drastic as going on a killing spree, in most cases they wouldn't have the care to do a lot of research if they already have a game that shows them acceptable methods.
The comments at the end are pretty accurate. The problem isn't with the violence in the game, it is in the person's want to commit the act. However, the detail with which a game goes into loading and positioning animations might be a bit too realistic for the goal of the game. Sure, information like that can be found for free, but when putting it readily into the hands of developing minds and replaying it for them time and again in a form of entertainment that is engaging and can create emotion, then it might not be such a good idea to make it point for point accurate.
