Operators have been given their chance to make a deal. Anyone left will be hunted down like a post ww2 nazi, even the ones in underground bunkers and tunnels.
https://rumble.com/vbc705-make-the-deal-mother-f-or-youre-going-to-die..html
Nah, that's contrived. There are many more easier methods of causing mass casualties. Injecting slow acting poison, radioactive sources, smallpox or just sterilizing you outright so you don't reproduce.
or the flu