Zombie wave?

In my past life there wasn't a lot of people but there was zombie waves. A zombie wave is when a lot of zombies come together and attack humans. They were even harder to kill and were the reason why I was the only human left in the world.

zombie wave is caused by a red moon. It only happens when a big mutant monster is slain.

Wait a second I haven't thought about it but mutant plant also counts. As I was thinking the moon above me started to turn red. I began to worry and immediately told everyone. People started to freak out. I calmed people down. We were in a safe zone so the zombies could not see us but there is a mutant zombie that can. One mutant zombie per zombie wave. That was what I thought until I saw it.