Ghost zombie appear when hitting a zombie

Put the summary of the bug you're having here

What actually happened was...:
A other zombie appear out of nowhere when htting a zombie.

Note:
It wouldn't do it often, but rarely does.
sorry for no screenshot. I didn't take a snapshot of the action.
It was probably either enforcement zombie or not.

Steps to Reproduce:
1. Hit a zombie.
2. wait for a time to come.
3. a ghost zombie appear when hitting a zombie.