In any tragedy people need some kind of scapegoat. It's REALLY hard for people to look into ALL of the reasons why someone did something horrible. It's far easier to say..it's guns! No guns for anyone! But then those that have/want guns say "No, it's not guns...it's video games.".
Now, we have an amendment guaranteeing the right to 'bear arms' if they want. Of course this was in response to the fact that early on in the Revolutionary war militias were very important. And they were civilians who armed themselves to fight for what they felt was right. Now the problem with any one person having guns...the fact that they exist...is that someone who wants one and shouldn't have one can get one. They may not be able to legally purchase one but they can steal one. And certainly those that do own them should be responsible with/for them. Even if you lock them up and keep the key on you..someone can smash the glass if they feel so inclined.
A lot of companies make money off of selling firearms. They have their own association! So they'll point the blame elsewhere. If you were to look into every person who committed any kind of horrible act since video games were actually a thing...most likely at least 80% of them will have played games. But how many millions of people worldwide play video games (even the most violent games) and do not commit any crimes.
The problem is that when you try to figure out why a person committed such an act you'd probably find some mental disturbance which may have been genetic or at least there from birth...and a whole slew of factors and things that happened to them to make them feel that killing others is the right course of action. But after a tragedy people want to know how to keep it from every happening again. So they'll point to single thing such as video games, guns, other forms of media, the internet or whatever the buzzword is at the time (bath salts).
The big problem is that it's RARELY ever ONE single thing that leads to someone taking such actions. You can ban video games but it won't change anything because it isn't the root of a problem. You can put a strict lockdown on gun use but they'll either still get guns or they'll use something else.
These are sick and twisted people with equally sick and twisted ambitions and while some people may feel that they can sleep better if one drastic step is taken to keep it from happening.... the fact remains that no single solution will keep such things from happening. Last I checked people have been murdering other people for thousands of years (Look! It's even in the Bible) before video games...before gunpowder. I'm pretty sure that Neanderthals use to murder each other with clubs.