I have a helping thought to the theory that Randy is 'helping out' Michael and the others. There is one other instance where a Zombie 'Helped Out' the Tower. At the end of season 1 when Tommy turns, he could have easily killed everyone in the hallway and tower. Instead he runs for the stairwell and dives into the flames, killing himself. It is mentioned a lot how smart Tommy is all throughout season 1. Maybe he was able to make choices as a zombie. Thoughts?