Again, that's entirely irrelevant.
It doesn't matter what criminals are going to do, because they are not going to follow the law.
Do you really think that people who are considering hunting down two cops and shooting them, are going to be shocked to find a law saying people engaged in premeditated murder are not allowed to have guns?
Again.... guns are not space age technology. We're not inventing a car that runs on banana peals and pop cans. We're talking about a fire arm that has existed for 100+ years now. You can MAKE ONE at home.
No law saying "bad people can't have guns" is going to stop one single bad person from getting a gun, anymore than alcohol during the 1930s, and hemp today.
Here's the thing. All the big time shooters, all got their guns legally. They didnt' steal them, they didn't make them at home.
They walked into a gun store and despite being batshit crazy, were able to walk out with a lot of guns.
Here's the thing. Japan has totally banned guns. They have 11 gun murders a year.
Yes, it CAN be done.
Apples and Oranges.
Japan and the US are completely different cultural systems. You generally don't see high murder rates from anything. Knives, Blunt Objects, anything.
They simply don't kill each other in Japan. It's an extremely homogenous society.
Again, you look around, and see Norway, with the 11th highest gun ownership in the world, and 8th lowest murder rate in the world.
How do you explain that?
Homogenous society with a strong moral code. Just like Japan. Nothing to do with guns, or gun control.
Second, when you say someone was crazy, you say that retrospectively. We know he's crazy now, but that doesn't mean anyone knew before hand.
A few years back I was working at a company where I was supervising a project, and the company hired on some guys to help out with the project. One of the guys, was perfectly fine the first week, first month. But over the course of several months I started noticing things. He started talking about how everyone was against him. How I was giving him the most difficult tasks (which the opposite is true. I didn't think he could handle the hard stuff, so I gave him the easiest tasks). Little insignificant things started ticking him off for no apparent reason.
I finally realized the guy was nutz, and he was going to blow up and kill people. I handed in my 2-weeks notice. I'm not getting shot over this fruit cake. The company was freaking out. "What do we have to do to keep you on?" I told them to get that guy out of my project. The moved him, to the front where he dealt with the production manager. Two weeks later, he flipped out on the manager, and was told to go home.
What's my point? With 20/20 hind sight, yeah how could they possibly not know that these people were nutz. In reality, you don't know. Nut jobs, do not tend to walk around with "I'm a fruit cake" stamped on their forehead. People that are fruit cakes, can act completely and totally normal and rational, until something snaps their brain, and they go bouncing off the walls.
The idea that "they should know!" is a statement by someone who has never dealt with these people. You don't know. They can talk, act, respond completely rationally. Go to the mental health facilities. They'll tell you. These people can be completely fine for months on end, and then something freaks them out, and they go loony.
Where you people get the idea that the FBI doing a back ground check, or the cashier at the gun should should magically know 'this guy is nutz'. You are wrong.
And honestly, we've tried it your way. We've tried banning guns in Aussie land, and the UK. What did that get us? Higher crime rates, higher murder rates, black market guns all over the place.
Did you know that right now, it is cheaper to get a semi-auto pistol in Australia, than in the US? You can buy a black market gun for as little as $100. The cheapest retail fire arm, last I checked was $200.
And you think you can ban guns, and lower crime? It's not happening. Ban alcohol again, and see how well that works.