Dean put his hands up. He held his gun, and he could have it down and in position to shoot within seconds. "Relax, I'm not going to hurt you, all right?" Dean brought his arms down, but didn't holster his gun. He might have been lying when he said he only had one bullet, and even while he was focused on her, he was on alert for additional zombies in the area.
He wasn't really bothered by her tone, expect that it implied she thought he might have an ulterior motive. He'd have killed the zombie whether the creature had marked her as prey or not. The fact she was there was incidental, but he figured it would be rude and hurtful to tell her as much.
"My name's Dean. I get my rocks off killing zombies, not molesting little girls. You got somewhere to go, where you can be safe? Maybe someone to look at those burns?"