I will not argue that violent games do to some extent desnesitize children. I'm and advent fan of these games (Please don't judge), however, I was taught from an extremely young age that life is important and how to discern fantasy from reality.
Each child will handle things differently. I dare ask those of the more mature generations that grew up with old western movies and so on why it is we didn't have all the problems of mass shootings back then if violent media plays such a strong role in degrading a persons moral fiber and ability to control their actions that they would willingly and easily take someones life.
Why? I say it's because we had parents that were actually parents, there was a time in this country where people cared for each other, looked out for each other. Society has become very self centered and selfish, it's all about what "I" want.
IMO it's not that guns or video games have become more prominent in society, it's that the value of family and morality as decayed to the point that society has become deeply ill. This is a social problem that did not exist 30-40 years ago.
That's my take on it, playing video games does not make you a murderer, it does not entice me to go out and shoot someone. It still horrifies me even after over a decades worth of playing "violent" games and watching "violent" movies when something like Sandy Hook occurs, let alone when someone meets their end too soon period.
IMO blaming the media and video games is almost as bad as blaming the gun for the evils that man commits, ultimately it's the individual who decides to pick up that weapon. Children these days are left to their own devices and the TV and video games have become the new nannies of modern day families. It's no wonder that these kids grow to be messed up, especially those that are not taught how to handle stress and the problems they encounter in life responsibly.
Just my two cents (or couple dollars worth)