Try 3/4 of the mass murders in the last 30+ years, the murders obtained their firearms legally. This is according to Mother Jones, which is about as progressive as you can get. https://www.motherjones.com/politics/2012/07/mass-shootings-map If someone breaks into my house and grabs a gun I left on the counter and shoots someone, that is not my responsibility...just as if someone broke into my house and stole my car, and killed someone drunk driving. This is also why bars aren't legally responsible for someone drinking in their bars and then going out and murdering someone via drunk driving. Now I'm a big believer of securing your firearms (especially among children, and we already have laws against negligence when it comes to children), but criminals should be at fault when they steal a firearm, not the owner.