He registers First Aid moving, but it doesn't quite click until he sees where the gun is being aimed, and the increasing tension of First Aid's finger on the trigger. For a brief moment, he feels his head exploding against a wall again.

Before he knows it, he moves out of the way, letting it clip his shoulder with a hiss, and lunges towards First Aid, hand -- no, chainsaw -- extended. And he revs it, catching the teeth of the blades in the cords between First Aid's shoulder and torso before pulling down with a snarl.