According to meta-analysis conducted by Dr. Christopher Ferguson and published in the Psychiatric Quarterly, there is no evidence of a connection between violent videogames and actual violence, leading many scientists to posit a difference between "real" things and "pretend" things.
"It is not hard to 'link' video game playing with violent acts if one wishes to do so, as one video game playing prevalence study indicated that 98.7 percent of adolescents play video games to some degree," he writes, "However, is it possible that a behavior with such a high base rate (i.e., video game playing) is useful in explaining a behavior with a very low base rate (i.e., school shootings)? Put another way, can an almost universal behavior truly predict a rare behavior?"
To control for the faulty assumptions, Ferguson looked at studies that correlated actual violence with videogame playing, and not simply "violent thoughts" or physiological measurements.
Turns out, there aren't that many studies of this nature (17 published studies over a 12-year period), and research Ferguson considered un-biased indicate a lack of causal relationship between playing violent videogames and actual violence. So there.