Document everything....take an afternoon and write it or type it all down...witnesses...times...etc...Mail a certified delivery receipt letter to your regional HR office and CC everything to corporate HR office...Use the Teamster's free lawyer consult and spend a half hour bringing an attorney up to speed (if you don't have a family lawyer already). Explain to the lawyer if the situation is handled to your satisfaction by the company you work for, you won't require his services. Let HR know in your letter that you are doing this. It will be up to you to reign in the lawyer if things are resolved...don't let him/her pressure you into a frivelous lawsuit that could end in your dismissal through some arbitration...You can also file a complaint at the Police or Sheriff dept...No charges have to be pressed, you can just file an official record of perceived workplace violence, just in case it happens again, you want a record/slash history recorded...In your letter to HR, you need to explain that you have a genuine fear, not only for your personal safety, but also the safety of your family...You have to take the supervisor at his word...he says he is going to make your life a living hell...remember he has access to your social security number, things that could be used to steal your identity, your home address, your personal vehicle parked in the parking lot while you toil away doing your job.
On a personal note, I have wanted to strangle managers from time to time over the years, and Lord knows they have wanted to do the same to me lol, but I would never tolerate a direct threat or especially the physical stuff, nor would I ever threaten or physically intimidate a manager or employee...99.99% of the people I work with, hourly and management, would not want to work at a company that either ignores or condones the kind of behavior you described. Am I naive...? No. I know these kinds of things must happen daily. We work in a physically and mentally high stress job. I just personally don't tolerate it, and over the years, my work group knows this.
That said, unfortunately, intent means everything. I have been smacked, punched, prodded, and hollered at over my years at UPS, but these were always by friends celebrating the birth of a child, the culmination of a saftey milestone, talking trash about this team or that Nascar driver...the intent was never to inflict harm or mental duress. The situation you described had a different intent that should not be tolerated at a company of professionals.
Intent should also weigh in on your judgement. If your intent is "revenge" instead of truly protecting yourself and fellow employees, then frankly, you should be shown the door right along with the dude that threatened you. In your dealings with HR, if it appears revenge is your motive, I fear you will be in for a struggle. Its human nature to not want to help a prick out for revenge (even if it is your job), I know I would not jump to it if I were HR and got a letter demanding the head of your "enemy" on a platter lol...If you are truly stressed and upset about all this, I think you will get a lot further if you are honest and open about this in your letter...
Good luck and God Speed...