I'm like, the last person who espouses PvP combat as a solution to things, but this guy...
I think the best thing you could do is rig his doss with like, all the white phosphorous. Enough to be damn sure anything biological is incinerated. Light the mother up while he's at home.
Then explain to him, carefully, out-of-character, that there's Pink Mohawk, and there's batshit insanity that's going to ruin the whole game for everyone.
And then offer him a retcon - make it a terrible dream, a prophetic vision of what would happen if he pursued in his insane quest for vengeance, in the most stupid manner possible, which he can abandon if he wants to keep the character, or offer to let him make a new character at the same karma and same nuyen the old one had.