@ General Zod: Yes, obviously, people who desperately want to own a gun will get one if they try hard enough, even if owning guns was illegal, but do you think the average Mr. Smith-type of guy would risk making himself a criminal in order to get a weapon for his own protection? I doubt it.
If all kinds of firearms were made illegal, and only a select few shady characters like criminals owned weapons, then chances are you'd get rid of a lot of unnecessary impulse killings - people who just tilt, find the nearest weapon that they have bought for protection, and let rip. Some people might feel insecure or threatened by the fact that criminals may be carrying guns out in the streets, but that's the way it is (more or less) in Europe - guns are, in most cases, illegal, and the weapon policies are strict. We don't have mass shootings like Columbine, Virginia Tech here, and smaller scale shootings are pretty rare. Coincidence? Possibly, but I think not.
Ditto.