Originally Posted by Shadow
Lots of good comments. For this particular one, they might be infected and if they are they won't kill zombies of any kind including the parasites.
The townies in question weren't infected with Zombasite; I wasn't getting notification that anyone was infected (this happens many times, so I'm not talking about a singular incident). But is it possible they were infected with something else? Yes, maybe. I'll have to look next time.
Would personality type have anything to do with it? Maybe ulterior motives? Could the townsperson nearest to the bug be subverting the town and bringing them in?