Not exactly a great argument since mass shooters come in all ages.I can tell you one thing I wouldn't want to be the one that sold an 18 year old a handgun and the next day he went and shot some place up with fatalities. The news media would be camped out on your frost lawn the next day.
So Jogun Seller, how do you feel knowing your gun killed 15 kids yesterday?
Why did you decide to sell that gun to him? The questions would just keep pouring at you from all sides and your face smashed up against on of those industrial size cameras.
NOPE! NOT ME!