Tbh, I think experience evolves life. What I'm trying to say is... that when somebody has a aggresive nature, that either can be stimulated or toned down. Certain experiences and methods happened in that somebody's life either stimulate or tone down that aggresive nature; this is different for every person, it's one of those things that make us unique and complicated beings. Anyways, I do think violent games can stimulate aggresion if that persons 'refencechart' (hopefully you know what I mean, can't get the English word for it) is completely messed up due taken experiences in life. Humans are emotional beings, and when you're not stable... you can very easyly be influenced. However, I wouldn't go as far as say 'games create violence' simply because that depends on the person - and luckyly most people have a decent enough sense of mind to know what's right from wrong.
I'm not trying to sway your opinion on firearm ownership necessarily, but mass media loves to paint an inaccurate picture of things. Let's not point the finger at guns or at violent games. There was something clearly wrong with this guy, and chances are he would have harmed someone in his lifetime, with or without a gun and without ever playing a violent game.
Possible, but given it he is an aggresive person with a twisted sense of mind and his father stimulating that by lockin' up what's so dearly to him, the game.. he figured where the game was, and stupidly enough the gun was right besides it. In a act of rage choices are easyly made. He made the wrong one.
About mass media en firearms ownership.. what says the FBI's report is completely true to fact? I might go far with this, but even in 'great' America propaganda lives. Sounds rather logical tho, the FBI wanting to create a sense of safety for America's citizenship.
/end rant - Heh, I got carried away. Forgive me for my broken English and conspirecy theories, haha.