I'm not clear, were you the DM or a player? In any case, the best way to deal with psychopaths is to treat them like psychopaths. You call the guards (if you're lawful or neutral), try to protect the innocents (if you're good or neutral), and if necessary take him down yourself.
If you're the DM, I'm sure there are well-trained guards, other heroes, high priests, bounty hunters, or LG mages somewhere in your world. If he gets tossed in the clink and beats up other prisoners, it's solitary confinement in "the box" for him. And probable execution the following morning.
Then you don't invite them back next time.