Video games are not the reason for violent children and Guns are just the weapon already violent children choose to use.
The blame for these killers should be placed on their parents and the society that forged them.
I remember being in school and the only thing that stood between me selectively shooting a bunch of bastards who took joy in making my life shit was the fact that I was unwilling to end my own life.
People should be asking why are these teenage gunmen willing to sacrifice their own lives after killing others "as it's the true source of the problem"
If I had to guess I would suggest that the majority of these mass shooters would consider themselves martyrs that are doing us a favor by killing people they believe to be nothing more than a negative impact to society because those people had a negative impact on the shooters life.
Hell even at the age of 30 the only thing keeping me from killing those I declare as unpleasant assholes is that I couldn't bring myself to commit suicide to avoid incarceration, however when someone is belittled to the point of being suicidal all bets are off.