If you tell an average American about scrapping the 2nd amendment they will go apeshit. So we dont want to do that. What instead should be done, is psychological tests measuring mental capabilities each individual owning a gun. Not just initially but every so often, 5 or 10 years. You dont get a sane person to come out and shoot everyone 'just because'. Surely, this method wont prevent occurrences like that but it definitely greatly reduce it.