If you're really interested in the latest game-violence/real-world violence causation study beyond just skimming the press article, you may as well go to the website of one of the principal authors, Brad J. Bushman.
Dr. Bushman helpfully allows the download of almost all of his peer-reviewed articles. I've snagged three of them that focus on videogames and will do my layman's best to go over them when I have the time.
Homework never stops.
Before I read these papers, I will mention that one thing I noticed in the studies I've read previously is the disregard for the actual incidence of violence and lack of correlating any increases of violence in specific demographics with other social factors.
For example, in the last six years the gap between rich and poor has widened due to disastrous economic policies. This kind of wealth disparity has been shown to cause an increase in crime, and these crimes are the type that aren't motivated by violence but often result in it - carjackings, home robberies, muggings. And because college is often out of reach and jobs scarce, this type of crime comes from young people - who happen to members of a generation in which almost everyone has played videogames.
In fact, the biggest difficulty in any media violence study is attempting to control for all the variables. Are they correlating with children who played sports? Are they identifying the type of sport, e.g., contact vs. non-contact. What about music choices? What about different kinds of abuse? What were their social groups and the interaction between them? What economic status?
Without a good control group, and with the fact that pretty much everyone from the last three generations has grown up surrounded by videogames, these kinds of studies are nearly impossible. Then there is the difficulty of classifying violence - is Mario violent? "Realism" is often touted as being especially affecting, but what is considered realistic? Mortal Kombat was called realistic, but nowadays it looks cartoony. The goalposts are constantly moving, so how do you even begin to discern a metric for realism?
Media violence doesn't happen in a vacuum. I'm not going to disparage the people who make it their life's work to study it, but I do find that conclusive studies tend to be anything but.