My ex threatened to kill someone too. I returned to save that person's life. I later ran away anyway, when things got too serious and violent. At that point, I feared for myself and that other person too, but I had no way to contact that person and warn him. To this day I have no clue if he is alive or not.
My ex started calling my voicemail from prison. I would hear this recording that the person calling me was in prison and to press #9 if I was willing to accept the call and pay for it. So I knew it had to be him. Sure enough, I called the prison and asked if he were a prisoner there and when they confirmed it, they even told me the charges: "Utterance of a forged document, concealed weapons and domestic battery" were the charges. I was not at all surprised! His threatening calls stopped at that point, of course and eventually the calls from the prison stopped also.
I ran into him about a year and a half later, while waiting at a bus stop. He ran up to me, hugged me and said, "Baby! Baby!" I told him I was not his "Baby" after ducking out of the hug. I told him I could not live like that. I did not elaborate, except to say that I did not want to be with someone who did drugs. He accepted it then, I think, as he never tried to contact me again. What a relief!!!
One of the reasons I think he had to accept it was that he was probably on Parole. That was my luck!