Evidently, Michael Bloomberg, the virulent anti-gunner who also happens to be a billionaire, gave Johns Hopkins University a metric butt-ton of money to conduct a study for him.
Who'd a thun, but the study determined that there is no evidence that assault weapons bans have any effect on mass shootings. Wow! No we know, assault weapons bans don't do anything. Except violate the rights of freedom-loving people. That's it, guys, the science is settled.