[deanhills]

But what is the origin on such violence in U.S? I don't think videogames are related. Maybe TV shows? Who know?

I'm wondering whether the root cause is social and family.  Family values are not what they were before, like looking after one another, and looking after one's parents and grand parents, so you find so many drop outs with grudges against one another and society in general.  To get a job in the US or Canada is quite something.  Like cut throat, particularly because of the over population in all of the big cities.  It starts even with children where they are taught to win.  So when you get to a job application there are probably tens of people who equally qualify for the job.  So you have to perfect your strategies with creating just the right style CV, cover letter, interview style (master all of the test questions) approach to employer and market yourself heavily.  Thing is there is so much stress doing that, that by the time the person actually is told that someone else got the position, they're fatigued and to stay in the game you have to be very strong and resilient. And that is just the start of it. If you do get the job, you've got to stay focused as you're still competing with many candidates who want the job and hoping you may fail. So you go all out at the job even if it means stabbing someone in the back. That's more or less the atmosphere with jobs in the US. Those who don't have the strength to survive this stress, get sick, go for drugs or whatever and develop all kinds of issues that create drop outs of them. They're the ones who can easily get to be violent.

You're right about guns being too easily available, but it will be difficult to remove it as it's an alienable right of every US citizen to bear arms.  The US has got as far as to limit those arms to certain ones, but those wanting Government positions won't advocate too hard against guns, as that may loose votes for them.  There's also the thing about self-protection.  If you're not allowed to have a gun to protect yourself, what do you do when someone who isn't allowed, but does have a gun, invades your home?  How do you defend yourself against it?  Also, with 50 states and 350 million people.  How do you legislate against gun ownership overnight?  Got a lot of practical common sense issues that if it would have been easy, the US would have done something about it long ago - but it is not as easy as guns are part of the fabric of US society.

So I'd say the root cause of violence would be families no longer staying together, and mad at one another, and producing children who don't have real mothers or fathers to emulate, or have mothers or fathers who are absent, or dysfunctional and some of them can't deal with it effectively.  That is probably the root cause.  Another one I'd say would be that even though every one is preaching against this, I believe that you do get people who have been born with a character that loves to hurt all living things.  Like born to kill.  I'd imagine playing games of violence would particularly wet their appetites for the real thing.