I'll preface this by saying, "Yes, I know, PF has not been formally diagnosed as a narc." Neither was CW. This is MOO.
Narcs CAN'T move on. Whatever the stakes are, custody, control, money, THEY must win, AT ALL COST. Sad but true. Not all narcs will murder but they WILL try to destroy you, either financially, emotionally, physically OR all three. AND, even if you come to your senses, find the courage to break free, they are NOT finished with you. Their behaviour is pathological.
Sometimes, on the flip side, are the victims that KNOW their life in in jeopardy (I don't feel KB knew), feel they have 'no way out' and they will murder the narc out of desperation. These poor souls will end up in prison too, because the narc has created myriads of "flying monkeys" that will be only too happy to tell everyone what a wonderful person the narc is and that the killer was crazy. Why? because the narc told them he/she was insane. Oh my, who told KK that KB was crazy and he was afraid she was going to harm baby K? Stupid question