He has federal charges for sending that letter to himself through the mail. That should earn him some time.
People don’t realize, messing with the postal service; using it for threats; they take it VERY serious.
I have a close relative that was on the receiving end of some nasty grams from some psycho and it was local PD, local postal inspector general; only reason FBI was not involved is because there was no actual “threat” in the letters.
That guy and his “bro’s” have some serious charges on their hands.