Just my opinion, but I'd say the officer startled the guy because of the AC units, he probably jumped, stood up quickly and the office mistook a took in his hand as a weapon and fired. Upon realizing his error he came up with a throwdown weapon and a story to cover his butt. To buy a handgun legally in most states requires paperwork, if it shows the gun belonged to the guy then maybe things happen the way the cop say's, but I'd bet they say the owner of the gun cannot be determined or that the gun is one that was stolen years ago and they will make up another story how this guy probably purchased it at a gunshow or a fleamarket. Only time and some digging will bring out the truth of what happened that night.
This is CABL.com posting #172483. Tiny Link: cabl.co/mS19