I disagree. Access to weapons is not what causes people to go on a murderous rampage, video games are not the cause either.
If we banned the civilian population from owning guns, that would be a very bad and debilitating thing. Why? Think about it. Owning a gun would be breaking the law. And who would not care if they broke the law? Criminals, the people who we actually don't want to own guns. And who would care if they broke the law? Law-abiding citizens, the people who we do want to own guns. Basically, if we make it against the law to own guns, we are taking guns away from the civilian population so that they cannot defend themselves, and making it so that only law enforcement(who are sometimes corrupt), military(who can also be corrupt), and criminals have access to weapons. I do not think that is fair, nor do I think that is a good idea. And if we banned guns from popular society, in movies, etc. then they would just use other, equally violent, things. It doesn't matter if they're beating someone to death with a piece of rebar or shooting them in the head with a Colt .45, violent movies are always going to exist, and they're always going to be violent. If you take away the rebar, they'll just bite people in the neck, or break their nose, or something. My point is, you cannot remove violence from society. It would be a massive waste of time and money even to try. There are plenty of people who go and watch violent movies, play violent video games, and don't turn into school-shooting serial killers. Those school-shooting serial killers are the exception to the rule, and the reason you think correlation = causation is because they're the only ones you hear about. You guys really need to stop watching so many Michael Moore documentaries.
And now this brings me to what I believe really is the cause of most school shootings: not any movie, video game, book, or any other fictitious universe. I present to you the theory that there are many things that can cause someone to snap and go berserk, killing innocent people. Here are the three reasons that I find to be the most plausible or commonplace.
1) Mental imbalance. They had some sort of chemical imbalance in the brain, a mental disorder, etc.
2) Bullied. They were tormented by a group of people at school or even at work, and decided to take their revenge.
3) Unhappy home/childhoood. They had parents who neglected or abused them, they were poor, etc.
There are other possibilities like these, but I think you get the point.
In my opinion, what we need to do as a society is, when the children go missing in the dead of night, stop blaming the scary-looking bogeyman, and start looking for the escaped convict who has put on a facade. That means stop taking the easy road out, and stop blaming the scapegoat. Sometimes the media instigates a moral panic, and sometimes the politicians are really just that stupid. In the in the 1970s it was heavy metal, in the 1980s it was Dungeons and Dragons, in the 1990s it was satanic cults, and now, it's violent video games(and Arabs, on occasion). All of these things are completely ridiculous, and none of them address the real problem. Murderers existed long before any of these things were even thought of, and they have and will continue to exist long after these things go out of style. Because murderers are caused by mental imbalances, anger(caused by torment dealt to them by other people), and depression. These three things will never go out of style. We need to stop blaming cultural scapegoats for our problems and trying to limit them, and instead try and create a more nurturing environment where human beings can be treated as such by other human beings. A violent, unhappy environment in real life is what creates murderers, not a violent, unhappy environment on TV or in a video game.