In the first Mission with screamers (creating pattern on building by laying explosive charges) all the zombies in the area that had been lying around stand up.
This also happened in quarantine zone. Actually I had camouflage on and shoot him without any noise, then the zombies stood up for no reason. Those already had been suspicious as they ALL had 3 pieces of loot and I searched them without any movement. There also had been one zombie in the little corridor to the room that I shoot when I came into the room (just to make sure he doesn't stand up) + I had the door closed. Anyways that guy didn't stand up.
So I want to know if anybody experienced the same.