re: Bump/Slide stocks are flying off the shelves

"Legally obtained" would mean they are documented. So that is one way. But that would only be valid if the shooter was apprehended. If not, no one knows to even look to see if a documented suppressor was used. So chances are that it has happened at some point in time.

Certainly murders have been perpetrated using an illegal suppressor. That's why all suppressors were illegal for some time.

In this case, I don't think a suppressor would have made a difference either way. At the distance he was shooting, with non-subsonic ammunition, the people on the ground would hear the sonic crack before they would hear the muzzle blast anyway. Having said that, my opinion is suppressors have a place at the range to control noise. That's about the end of it. These guys that say they are going to pick off more feral hogs because they don't hear the shot are probably right to some degree. But that isn't a practical reason for allowing suppressors to be legal.