"went bonkers" , "flew of the handle", "went postal" The "postal" refers to the fact that about 10-15 years back, there were a series of abut 2 or 3 incident where employees that had been fired of the U.S. post office came to the office they worked at and shot several people (each). None have happened since, but the incidents got such an amount of coverage that it stuck in peoples minds and became part of the language.

Other ways of saying this is: He lost it, he went nuts, he went berserk.

A slightly older saying with the same meaning is "flipped his lid". You can also just say "flip". So I think the original image is someone's head actually having a lid like a saucepan. So it flips when you boil over, explode, lose your temper. I'm sure there's a cartoon around of this image! "Out" and "off" turn up amazingly often in modern phrasal verbs - I think many are still not written down as they're constantly being created. (Just my thoughts.)

Hi... . flip out - react in an excited, delighted, or surprised way; "he flipped when he heard that he was accepted into Princeton University" flip react, respond - show a response or a reaction to something 2. flip out - go mad, go crazy; "He flipped when he heard that he was being laid off" flip change - undergo a change; become different in essence; losing one's or its original nature; "She changed completely as she grew older"; "The weather changed last night"

He went crazy. He lost control.