Thanks for all of the advice so far. DS I am leveling with you when I say I have never done anything-absolutely nothing- before that I have ever gotten a warning letter before.
What I got the letter for was this: I was working on Friday night and the sort had been called down and my fellow co-workers and I were trying to finish up the packages we had (I work in International ). I had just finished the last package I had and got read to toss the package (I know hand to surface) onto the belt. Just as I did this, one of my coworkers came up to gather the invoices. Well the box hit her, unfortunately it hit her in the face

. The box was a small and weighed only 1 to 1-1/2 lbs. Mind you I didn't throw this pkg with any force. Just enough to get it to the belt that is about 2 ft away from my work station.
I immediately realized the stupidity of my actions and quickly went to assist her. She said she was ok and it just stung a little bit. We both went about finishing up for the evening and I continued to check on her and she still said she was ok.
Now the department supe comes in and notices her sitting at the desk and asks her what happened and she tells him. She told him that she was ok and didnt want to file an accident report
Now this is where it gets complicated. This same girl is on TAW for an injury that she sustained over a year ago. She is currently seeing UPS doctors for her condition (supposedly a herniated disk in her back)and she has retained a lawyer because UPS is fighting her over her claim. Since this is the case, the dept. super though it best to write a report of the incident,(so she couldn't come back later and say she has sustained more injuries and it was related to the previous injury). So he talks to his boss and his boss wanted to write me up but the dept super said he wanted to "retrain me".
So that is what happens. The dept. supe fills out the report of what happened and notes that he has instructed me on proper methods and I have been retrained. We all though it was the end of things, until I come in Monday and it hits the fan.
Seems the girl that got hit with the box, claimed her neck started to hurt and she went to the E.R. Now UPS is stuck paying for an ER visit that they said should have never been.
They brought me into the office Monday with my steward (alternate steward actually who isn't very good at the job and the regular steward is on vacation

) , my shift supervisor and his boss. That's when I was told that I could lose my job and that this was my final warning letter.

I pled my case and told them that I fully understood the gravity of the situation but it was an honest to god accident that I truly regret and would never happen again. (and it never will again)
The shift supervisor stood up and told his boss that I was "not a problematic employee" and that I am "a very concientious worker who follows all work methods,my attendence is very good and my job performance is above average" My dept. Super even pled my case and backed up everything that the shift super had said but to no avail.
I recently found out that the District Manager found out about what happened and she isn't too happy with the whole situation. She is a "hard-nose" and several other people in my building have had run ins with her. And now its my turn.
Now I know this situation isnt the very best but did it warrant me getting a final warning? I didn't steal anything, I wasn't drinking on the job, no one was permanently disabled, disfigured or killed. It was an honest to god accident that I feel deeply sorry for and will make sure will never happen again (whether or not had I gotten the letter).
Am I wrong in thinking the discipline is a bit extreme? Am I wrong in believing that UPS didn't follow proper procedures pertaining to the warning letters? I just want to find out if this is what really should have happened.
Thanks for all your help. People like you are one of the reasons I joined the Brown Cafe forum in the first place.