Statistically there is a 100% chance everyone is going to die at some point...
Constitutional gun protections are a hotly debated issue...I won't go there. But what I can say is that as soon as you start restricting gun ownership in any way, its a foot in the door and it only gets worse from there. So while I completely agree with some of the above posters regarding inept gun owners and necessary training, I don't ever think people should be forced to get weapons training before buying a gun...it will simply invite more regulation and more restrictions.
I do fully support voluntary weapons training...something akin to the Motorcycle Safety Course in CA. A voluntary class you can take before getting your MC license. Completing the class successfully gets you a few perks, like lower insurance rates, etc.
Offer a low cost weapons training course that's state sponsored, and completely optional. They can take the class before purchasing a gun, learn basic weapons responsibility, and as a reward they can get some mild perk during purchase...say a few days off the waiting period, etc.
Or just look at it this way. Selling guns to idiots is a good way to clean out the gene pool. Assuming of course they don't shoot someone else....
You could make it a law that there are no accidents with gun use. If you kill someone with a gun on accident, no matter the reason, you are getting charged with manslaughter. Might remove some of the motivation for certain types to buy weapons. Of course justified killings would still be legal...