I let my son believe zombies are real and he might become one. It traumatized him until he was about 7 years old.
What did you tell him that traumatized him?
I told him you become a zombie right after your teeth fall out and he didn't want to show me that he had lost a tooth.
I think it's totally inappropriate that you scared your child by telling him that he might become a zombie. It's awful to let him believe such a thing. You should have told him the truth once he became so scared.
I don't think I did anything wrong. I gave him a bedtime story every week and that's all it took.
There are other ways to tell your child a bedtime story without traumatizing him. Unfortunately, his fear might stay with him for a long time. Hopefully you can help him repair that through better stories.