Claim: violent video games don't correlate to mass shootings
This claim is mostly true.
The CNN article states that, "While some leading psychological organizations in the US say that children should not play violent video games because it may lead to aggressive behavior, there are no findings from research that demonstrate a direct connection between people playing violent video games and mass shootings."
The information from CNN aligns with a review by the American Psychological Association (APA) in 2015. In the review they determined, "Violent video game play is linked to increased aggression in players but insufficient evidence exists about whether the link extends to criminal violence or delinquency"
While violent video games are linked to aggression there is not enough evidence of a link to criminal violence to correlation violent video games to mass shootings.
The review by the APA was conducted on research published between 2005 and 2013 including more than 150 reports published before 2009.