@AthenasOwl Do assault weapons account for the difference?
I don't really understand the assault weapons ban, or at least the way it was written – I could see banning firearms altogether, or banning certain calibers, but who cares if a mass shooter has a barrel shroud and a flash suppressor or not?
I know some mass shootings used "assault weapons", but it seems like the shooter would have murdered just as many people without them in most cases. Different features, not covered by the ban, seem more important: Bump stocks are now banned, for example.
So... I'm thinking something else changed in the last 15 years to account for more deadly mass shootings. Media coverage seems to be another common answer, but that doesn't seem convincing either.