My condolences to the parents, but this kid was nuts because of physical brain deformity or outside mental pressure, and was not made crazy by a video game, although placing the blame for the horrible incident on a computer game rather than their own failure to notice the kids tendencies and get him counceling. If he was playing the game so much, that behavior should have been a trigger that they should at least explore any anger issues he might have had. The fact that he shot family and not random strangers (as you would in the game, incidentally) makes me think that there are more issues to this than just gaming.
Is the game violent, on the order of the horrible "Going Postal"? Yes. Would I allow the game in my house? For me, certainly not. Is it my job to be aware of what my teen is involved in, to the point of knowing if my kid is dangerous in any way? You bet!
Game over. Sad, but not the fault of the programmers, even if they should have higher values than to make such a game. I would be willing to wager that said perp had violent DVD's, enjoyed slasher movies, and other violent fare. The gaming was probably only part of the whole.
According to those who knew the kid, his parents were evil incarnate. They pretty much got what they had coming, though that does not make it right.
I remember one unfortunate ad for children's software. In the middle of the "Builder Bob", "Reader Rabbit", etc, the hapless compositor included "GTA: San Andreas"....