I've had a PA License To Carry Firearms for many years and to the best of my knowledge, PA has no requirement "to declare" if in the presense of an LEO, especially in a "social situation" like the parking lot, with a mere exchange of pleasantries having taken place?
The desire to have backup/witnesses for an official stop might be in play, but am puzzled why the officer didn't just ask about a license to carry while in the UPS lot, if he noticed the firearm? "Yes I have a carry permit and here it is". End of drama. Most of the cops I know here would've done that without any hesitation, if they were concerned about the firearm being carried.
The situation could've been settled right then and there, without the necessity of driving about, calling for backup and making a stop.
Sure sounds like the officers had expected him to continue on to his stated destination (the Post Office) and then pinch him for violating USPS regs when he entered the lot?
PA is an open carry state and there is continuing and often heated discussion on that subject. Some feel determined to flaunt their right to carry openly, which often leads to confrontations with law enforcement. I went to all the trouble of getting the LTCF, so I could carry concealed. Confrontations with LEOs, ain't a part of my makeup. Fewer people that know I'm packing, the better, in my opinion.