I mean.. if you play video games for hours and hours, your brain will likely learn to play videogames better? Sure. I hardly see a correlation to mass murder here.
If you believe that action repetition is to blame for rewiring people's brains to be more efficient at mass murder, why not blame the military, or hell, why not just start picketing outside your local airsoft or paintball places?
edit: he'll into hell. I blame autocorrect.
I'm genuinely curious to know where in the world you live. I would be horrified if someone was peeking under the stalls or bothering people by knocking on the doors.