It’s rare but there are zombies who manage to rise above their undead state and become leaders. These characters are pretty common in the Romero zombie stories. In Dawn of the Dead we saw Flyboy suddenly become a leader when, as soon as he turned, he lead the zombies in the mall through the false wall to where the other survivors were hiding. Romero seems to grant his zombies a high degree of tool use and intelligence. It also seems in the later movies that the zombies are somehow growing and developing. They are starting to come back to themselves in some ways. And so Big Daddy comes along and leads an all-out assault on the survivors city with weapon in hand. He calls out, well he moans out battle cries and even instructs other zombies in what to do. He showed compassion by trying to help the other zombies and keep them from getting killed. This level of intelligence is something more befitting a monster than a zombie yet there we have it in the heart of zombie country.