Zombies are coming from everywhere as soon as you antagonise one. This is not just zombies within the general vicinity.

What I expected to happen was...:
Hit one zombie and have four or six in the area start coming towards you and attacking.

What actually happened was...:
Seems that zombies are coming from beyond the range where a Ender Man would be antagonised. There also appears to have been an increase in the number of zombies in the area.

Steps to Reproduce:
1. Antagonise one zombie.
2. Keep killing zombies until you are crowded and overpowered.
3. Die.