As a game developer, I was expecting this subject to come up. I can see how a lot of people could hold the games industry responsible for "training" this psychopath but let me point out this one fact.

All excessively violent games are rated Mature. That is equivalent to a rated R movie. If you see a 10 year old playing Call Of Duty, that child has parents who bought that game for them.

I grew up in the times of Mortal Kombat being demonized for everything and guess what, I couldn't buy the game at first. My parents waited till I was a few years older and explained how this fantasy violence wasn't ok in the real world...I think I was around 14 at the time? Point being, parents should not be buying extremely violent games for their kids...and if they do they should have a few very long talks with them. Also game shops aren't permitted to sell them, and online download software like Steam makes the account user verify age with each purchase. We developers of mature rated games ,make games for people our own relative age... 17-30+

Be a good parent. Because I'm disgusted when I see a mature game in the hands of a child... To me it's like handing them a pornographic magazine and expecting them to figure it out themselves.

A list of a few games out that are rated mature and not meant for kids:

Mass Effect series
Call of Duty series
Assassins Creed series
Far Cry 3
Dishonored
Diablo 3

If you see anyone under the age of 17 playing these, know that the parents bought it for them or gave their consent online for download.