gone postal

Verb

go postal (third-person singular simple present goes postal, present participle going postal, simple past went postal, past participle gone postal)

1. (US, informal, intransitive) To become aggressive and erratic, especially due to stress; specifically, to carry out a shooting spree at a workplace environment; also (more generally) to become very angry; to lose one's temper.
   • Violence that spills in from the streets may be less worrisome than the worker rampages, to judge by the attentive audience of personnel managers (and the consultants available for hire) at "A Growing American Phenomenon: Workplace Violence." The symposium was sponsored by the U.S. Postal Service...1993 December 17, Karl Vick, “Violence at work tied to loss of esteem”, in St. Petersburg Times, St. Petersburg, Fla.: The Times Publishing Co., →OCLC, page 4A, column 1

   Synonyms:

   run amok, crash out, Note: All terms are idiomatic unless stated otherwise., blow a fuse, blow a gasket, blow one's stack, blow one's top, cut up nasty, cut up rough, do one's block