In my opinion, it was the threatening remarks John would constantly make about killing Ross and Fordham that ultimately cost him his life. I believe if it was a deal somewhat on the governments part to use John to track his old gang would grant him a pardon it would have NEEDED to be documented somehow. And perhaps if John would have just done what they asked and never took too much pride in himself to insult them and threaten them, he could have had a chance to live with his family how he wanted. But Ross used John’s words against him.