Doesn't sound like the person I figured he was.
My suggestion for negotiation with a deadly hostile is to assert that your first, best, and final offer is they get to live so long as they immediately stand down. Sort of like a doomsday device in Dr. Strangelove. Make it clear that crossing the red line guarantees their misery.
Here was one of my favorite episodes, and it occurs to me it's almost entirely due to the section that starts at 35:42.