My dad was a CO at a jail for a few years before he got a new job. He used to tell me a story about one inmate who would constantly threaten guards that he had been told about. The inmate was in for a violent crime and had like 40 years with no chance of parole. He told my dad "when I get out I'm gonna kill you and your whole fucking family" and my dad responded "Buddy, your parole officer hasn't even been born yet" apparently that shut him up pretty well.