Not sure how it happened. I placed a bounty on him after he kept killing me 100 times over. He was also battling the cops and chops. So somehow I was able to get close to him while he was shooting elsewhere, and kept doing melee's over and over while his auto aim was blasting the cops instead. Low and behold, after a few more melee's (with the butt of my gun), GOD Mode is dead and I got the $9000 bounty I put on him back. Lol. I left the session right away before he could grief me even more.
It felt good. It really did. Try it and see if it works for you.