Video games are typically restricted by ratings, so they aren't any more to blame than movies or TV.
There's other factors at play here, and you certainly can't blame just one (although perhaps not all either):
*) Parents don't discipline enough, because the government won't let them
*) Parents don't discipline enough, because they indulge themselves too much
*) Parents don't discipline enough, because their only parent (or both parents) work long weeks (50, 60, 70 hours, and sometimes have to drive a long way)
*) Parents don't provide enough for their kids, because they use it all on themselves
*) Parents can't provide enough for their kids because of unemployment or crappy wages
*) Parents discipline too much, and so their kids act out
*) Parents discipline violently, so their kids "punish" others violently
*) Parents act violently, so their kids follow in kind
*) Their peers act violently, so they follow in kind
*) Media (News, TV, Movies, Video Games) that parents aren't able to censor makes the kid aware of violence
*) Teachers and other faculty that don't respond to behavior appropriately (some will blame the "new age" school of thought while others blame the "old school" approach to problems)
*) Kids feel they have nothing to live for (which may or may not be rational), so they act out (potentially indiscriminately)
*) Drugs (media sometimes triggers this, but it's typically an emulated behavior from peers or parents) make kids do stupid things
*) Terrorism reinforces the idea that violence solves problems, by killing innocent people
*) The government reinforces the idea that violence solves problems, by going to war and torturing prisoners
*) Kids, like just about everyone else, are ignorant, selfish, hateful
I could go on.