Talk to either your sort Union Steward or a driver Steward. A lot of times you don't need to file. Your Steward can have a talk with either the FT sup or the Manager and this stuff will stop.
that.
I have a good working relationship with most managers in my building, but I would absolutely file on that supervisor just to take another scalp. Throwing packages at an hourly is unthinkable in a place of business and a supervisor who does that doesn't deserve to work at UPS (or anywhere else, for that matter.)
When you have workplace violence at UPS, always do ALL of the following:
Grieve it under Company Policy/Article 37, Section 1 (with witnesses)
Give a report to loss prevention/security
Report it to HR/Ethical Complaint line
Verbal harassment is bad enough, but there have been enough cases of legitimate physical supervisor-on-hourly violence in my building just in the last two years that it absolutely can't be tolerated.