Wiktionary
went postal
vb. (en-simple past of: go postal)
Usage examples of "went postal".
In a postal sorting station in Phoenix, Arizona, a man went crazy, went postal as they said on the evening news, and shot Terry “The Troll” Evensen, a morbidly obese, awkward man who lived alone in a trailer.
He was already self-conscious about it, so when the stool broke beneath him he went postal.