Why was the postman traumatized?

Why was the postman traumatized?

Because he was given the following threat:

You are not wise enough to fear me as I should be feared.

Upon him I will visit Famine and fire, till around him desolation rings and all the demons in the outer dark look on amazed and recognize that vengeance is the business of man.

I will flay the skin from your flesh, the flesh from your bones, and scrape your bones dry. And still, you wouldn't have suffered.

I will show you fear in a handful of dust.