I think the point is 20,000 rounds is absurdly too much ammo.So 20,000 doesn't seem like enough ammo for a mass shooting?
Im sorry but be rational.
One loaded gun with threats is enough.
I find it hard to envision a mass-killer trying to go nuts while pushing a pallet with a quarter ton or more of ammo on it.
It really doesn't go well with the high-speed/low drag image these guys have of themselves