New Orleans, 1973. A sniper (and by no small coincidence, a black militant who Bobby Rush probably mourns to this day) decides to make his stand atop a downtown hotel. NOPD officers are outgunned, having mostly revolvers and riot shotguns. Citizens carrying cased hunting rifles arrived at the police barricades, offering to either use their rifles for the police, or to allow the police to borrow the rifles.
The sniper is eventually killed by a police officer shooting a *privately owned* M16 from a helicopter.
Yeah, it was a different world then - but in general you still kill a sniper WITH a sniper.
Well, the most famous, in my opinion sniper vs. private gun owners was Charles Whitman, atop the UT tower in Austin.
Lots of locals showed up with deer rifles and scopes.
While this cover fire is credited with keeping his head down and limiting his free shots, only cops storming the observation deck finally took him out (though there was a private citizen who went up with the cops, he was not allowed in the final push on the deck.)
If that happened again, all of the citizens providing cover fire would've been arrested and their guns confiscated while the sniper kept killing, and the death toll would be used as evidence of the need for outlawing guns.