Unless you're already experiencing anger management issues, violent video games will not make you more aggressive.
At least, that's the conclusion of researchers at Villanova University, led by Prof. Patrick Markey. The study, which measured the responses of 167 students who played violent games like Doom 3 and Return to Castle Wolfenstein as well as non-violent fare such as Tetris Worlds and Project Gotham Racing. Said Prof. Markey:
So probably what's happening is these school shooters aren't doing the shootings because they played the violent video games. They're doing the school shootings because they are angry and maybe they've been provoked in life. Perhaps one of these provocations might be about video games but there's all the other daily provocations that happen. So it's not the video game's fault for these school shootings. It's the person's fault for these school shootings.
The news of the research goes back to mid-April, but this is the first we've seen of this video report.