On August 20, 1986, part-time mail carrier Patrick Sherrill walked into the post office in Edmond, Oklahoma, and opened fire on his colleagues, shooting 20 people and killing 14 before turning the gun on himself. It was the first mass shooting by an individual in a US office workplace environment, and it sent shockwaves through American working life.
The massacre gave rise to the phrase 'going postal', a term for sudden, explosive workplace rage. Between 1970 and 1997, more than 40 people were killed by current or former postal employees in at least 20 separate incidents, cementing the phrase in the English vocabulary.
