go postal

The phrase "go postal" is an idiomatic expression that means to become extremely angry or to lose control of one's emotions and behave violently, often specifically in a workplace environment. It derives from a series of incidents in the United States during the 1980s and 1990s where some postal workers, under extreme stress or frustration, committed acts of violence against their coworkers or customers. As a result, "going postal" has come to represent any sudden and uncontrollable outburst of aggression or rage.