Well, that knocks out BY luring her to his workshop underneath the school and gassing her.
So, considering how many shots she has, I'll still give it to Big Yellow here. Considering she would think it was simply someone inside a suit, she wouldn't go all out on trying to kill it. Plus, if she does shoot, she doesn't seem like the kind of person to go for the kill immediately.
Big Yellow, on the other hand, is an opportunist, and likes to use people's assumptions about him against them. I can see her shooting him once, him slinking away, leaving a trail of "blood?", and then pulling the same stunt on her that he pulled on Willie, taking off his head, pretending to be an empty mascot outfit, and when she investigates it, he gets the jump on her.
Now it is possible for her to potentially kill him with the gun, nothing says otherwise, but I feel like this is one of the more realistic scenarios, considering the personalities of both characters. So, the smelly mascot wins out here unless other people have something else to say.
