A: What happened to Bob? I ran into him at the supermarket yesterday and obviously he was not quite himself.

B: The manager knocked him for a loop by firing him on the spot last week.

Note: This idiom means “to shock, surprise, astonish, or bewilder one, especially in a distressing or upsetting manner.” People also use “to throw someone for a loop.” These colloquial usages, dating from the first half of the 1900s, allude to the comic-strip image of a person pushed hard enough to roll over in the shape of a loop.