If one has raised a child or is raising a child and doing such a god awful job at it that exposure to violent video games, violent movies or firearms will turn them into a mass murderer I would say the game, movies and guns should be the least of their worries.
Like many I had access to guns as long as I can remember. I also watched violent movies and played some pretty violent video games, though they did not start getting very realistic until my late teens. That did not convince me that the morals or ethics I was taught by my parents were wrong and that I should go shoot everyone the bullied me or angered me in some way.
I was hoping all of this gun control nonsense would lose some steam by now. I suppose it has in many places, but not up in the NE.