Going postal

Rare card · No. 66645

Going postal is an American English slang phrase referring to becoming extremely angry or uncontrollable, often to the point of violence, and usually in a workplace environment. The expression derives from a series of incidents in which United States Postal Service (USPS) workers shot and killed people in acts of mass murder. Between 1970 and 1997, more than 40 people were killed by then-current or former employees in at least 20 incidents of workplace rage.

Read on Wikipedia