As everybody else has said, Workplace Violence. They are gone. There will be no re-hire, there will be no back pay. They can go to the panel all they want, but it's not going anywhere fast.
Furthermore, if something comes up, UPS doesn't expect you to get beat on, but at the same time, the second you fight back, you're gone.
Best Practice, yell for help, while putting something (boxes, Package Car, Belt) between the two of you. Ensure that your hands are open, that you aren't making a fist and keep yelling and saying "calm down".
Don't push, shove, hit, lay a fist on the other person. Keep your hands outward towards the other person and keep yelling for help. It's not worth your job. You are not going to get it back. You are not going to get Unemployment.
As far as "ratting people out" if you come across a situation where two people are fighting, break it up and get management involved. This is not High School. It needs to be dealt with appropriately. There is no Brown Line, as was pointed out this isn't a gang. You aren't trying to get promoted or forget your "brothers or sisters" you are protecting the job site and this needs to be dealt with.
Sadly Zero Tolerance isn't always that, but none of us are perfect either. If somebody here is perfect and without fault, keep challenging instances where it hasn't been addressed fairly, otherwise, keep quiet. Let him who is perfect throw the first stone.
Dirty Moose - Even though you are not going to lunch with these people any more, in my mind it needs to be dealt with. You should pursue it with your OCS and the driver involved needs to be dealt with appropriately. It's not a matter of you costing him his job, HE COST HIMSELF his job. There are a number of people lined up waiting for the job. If he is acting like that in public towards a co-worker, he does not need to be working for UPS. If he displays that behavior towards you, what's happening in front of the customer?
Folks, I've come across instances where drivers have threatened to kill customer's dogs, kicked packages across yards or docks in disgust of the customer, gotten in the customer's face and gotten physical with customers, cursed them out, told them they hope their business goes to a bad place, the list goes on.
You go back and look at what happened in the past and in a lot of these instances somebody comes up and says "Ohh yeah, they were fighting with another driver, but we never reported it" or "Yeah, he kept threatening people at work, but I didn't want to say it". What happens in the Brown Package Car, doesn't stay in the Brown Package Car if you know what I mean. It is going to spill over in front of the customer.