What is/was the thing about armed postmen in the US?

Question

Since I was a child, I was intrigued by two similar apparent inside jokes that I never understood:

• in an episode of "The Simpsons" when Ned Flanders runs amok, he shoots various people from a church tower. The only one to fight back is a postman that is surprisingly armed.

• in the dream sequence of the third movie in the "The Naked Gun" trilogy, Frank is attacked by a group of heavily armed postmen.

I would consider armed postmen an absurdity, but why postmen in two completely unrelated jokes? Was there some public debate about armed postmen at some point? Are they even armed under some circumstances?

Answer 1

"Going Postal" became a meme 20+ years ago for aggressive or violent behaviour...

From Wikipedia

Going Postal

The expression derives from a series of incidents from 1986 onward in which United States Postal Service (USPS) workers shot and killed managers, fellow workers, and members of the police or general public in acts of mass murder. Between 1970 and 1997, more than 40 people were killed by current or former employees in at least 20 incidents of workplace rage.

No, USPS employees are not armed and it should be noted that..

The [US] Post Office has been a “gun-free zone” since 1972 when Congress enacted the ban after a string of postal work-place shootings. In each of the 6 major shootings, it was not the average citizen that went on the rampage, but rather the Post Office’s past and present disgruntled employees! This is where the phrase “going postal” came from.

^{Opinionated Source}

Indeed, the clip from The Naked Gun they are specifically referred to as "disgruntled postal workers" and are just another piled on threat Frank Drebin is facing...

I would suggest that the "joke" in the Simpsons is that the last person one would expect to be armed is a Postman.