An oldie but a goodie...Ryan pisses off customer: violence nearly ensues

I am going to describe a transaction that happened at work a couple of months ago and for those who are anticipating a story about an insane asshole, I promise not to disappoint. I had a line of customers, the radio was on, and I was drumming on the counter as I typically do when waiting for somebody to pay. This is not an exaggeration as I would never embellish anything for the sake of humor.

Me: Just that?
Customer (On his cell phone): Yes
Me: $1.37 (Starts drumming on the counter lightly while anticipating dinero either being chucked on the counter or if hell freezes over, ending up in my hand: see rant about how people suck if you don't understand)
Customer: Hold on, I can't hear you (to friend on phone. He then hands me the money and I bid him adieu)

Fast forward 10 minutes
A man enters the store, and I do not recognize this man because it has been 10 minutes
Customer: Is your manager here I need to talk to him?
Me: HER name is Billie, and she is not in, is there something I can do for you?
Customer: No, I need to tell your manager what a rude fucking asshole you are

Normally me, being the hot head I am would not put up with this verbal abuse and at this point would throw him out of the store, but anticipating a good story I allowed him to remain in the store.

Me: Sir, what did I do to wrong you?
Customer: You were drumming on the counter like a rude motherfucking dickhead while I was on the phone. Is that fucking considerate? Is that polite dickhead? You need to get some motherfucking manners and decency.
Me: Sir, in all due respect it is impolite to be on the phone. Furthermore there are signs posted that say I shouldn't even be waiting on you while you are on your phone, so I did you a favor.
Customer: You motherfucker, give me your fucking manager's number. Next time you drum on the fucking counter while I am on the phone I will come over the counter and split your fucking head open.

I gave the customer the number and he left after this. In retrospect I should have either invited him behind the counter, or called the police, I am still not really sure. Bottom line: People are lunatics. Reminder: This is a detailed description of what happened verbatim. Nothing has been embellished. You tend to remember exactly what is said when you are threatened.