People will find a way to kill others, no getting around it.
Death is required in our society and our species, not just by old age, but by murder and war. We've been at war and murdering people since our race started. It's what we do, and we're really really good at finding new ways to do it.
Besides, the earth is already overpopulated. Between cancer and other illness, natural disasters, accidents like car crashes, things like smoking and other drugs, along with the large sum who get shot yearly, the earth is still very overpopulated. By nauture we die and we kil leach other, use drugs and die or whatever, so.. saying guns kill people isn't a very valid argument for a reason to ban it, when pretty much everything on this planet kills people.