I was in a town outside of green mountain when suddenly I flinch backwards and hear the hitting noise. Since there was nothing around me, I ignored it, but then it happened twice more, my screen was noticably grayer and I started bleeding. I then span around in a circle shooting(because I'm pro) but I could still hear noises so I ran away and logged off. It hasn't happened since, but I do hear zombie noises randomly when running.