As there were too many enemies, those higher leveled zombies soon gave up on fighting each other and rushed straight at the barbed wire which separated them from the middle area, then tried to climb up. One zombie climbed up first, but the other immediately dragged it down and then climbed up itself.
Level-two zombies were as nimble as human beings, but not smart enough. They were simply trying to climb up, holding either the barbed wire or the other zombies. Unlike them, level-three zombies were either stopping each other from reaching up or deliberately dragging down the ones who were climbing.
At that moment, a staff member threw a dose of antidote down to the middle of the square along with a fireball.
Boom! The fireball and the antidote hit each other and exploded.