Word for going crazy

What is a word which describes when a person loses it, when they reach their limit or pass the tipping point? I'm trying to use it to describe a person's transition from sane to insane. For example,

Dick Prosser's (transition to insanity) was accompanied by a ...


You might use breakdown or crack-up.


How about derangement / derailment?

Dick Prosser's derailment was accompanied by...


How about

Dick Prosser's descent into insanity was accompanied by...