Fire and /kill damage will cause zombies to spawn reinforcements

Incomplete without a description as per the Bug Report Guidelines:

Next, try to explain to us in the bug report's description what is actually broken. Be as specific and detailed as possible in the description. Think about the question "what is actually broken?" and provide us with your answer.

If a description is required, then why isn't it one of the "required fields"?

Zombies/ZombiePigmen spawn rienforcements when needed. So this means it not a bug nor glitch. Its part of vanilla

15w43a

Likely also affects cacti.

Seems to be fixed in 1.9.

Please make sure your test had doMobSpawning=true.

Yeah, it did. 😛