go postal

go (in the sense "become") + postal; from a rash of incidents, mostly gun violence, perpetrated by disgruntled U.S. Postal Service workers on co-workers in the United States, beginning in the 1980s (see quotations)

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

1. (intransitive, chiefly US, informal) To become erratic and aggressive, often by carrying out a spree shooting at a workplace environment.
   • 1993 Vick, Karl “Violence at work tied to loss of esteem”, in the St. Petersburg Times, December 17, 1993.

     The symposium was sponsored by the U.S. Postal Service, which has seen so many outbursts that in some circles excessive stress is known as “going postal.” Thirty-five people have been killed in 11 post office shootings since 1983.

• run amok

• go postal at OneLook Dictionary Search

• goal post, goalpost