Well first of all he shouldn't have made himself at home and opened the glove box, I'm assuming he was also taking a little peek to see what was in the glove box possibly looking for something illegal Illegal search and seizure warrentless search). He could have just as well given you the mags and ammo ( all seperated). Secondly he probably ran the serial number to see if the gun was stolen.
You might want to call Internal (without initially giving his name ) to see if everything he did was standard procedure. If they determine that it isn't they would as you his name and badge nuumber ( usually on the citation ). Then let them deal with it.
Sounds like he was looking for something illegal to get an arrest, but for the most part you did the correct things.
It could be that he was fishing for something, but The feeling I got from watching him was that he was unsure of what he was supposed to do and just made some honest, albeit serious, errors. The Hammond PD website doesn't give any options outside of filing a complaint. I plan to file the complaint but it will be against the procedure and policy as opposed to against the officer. It's my judgement that he was following instructions. Yes he should know better but I don't want to get him in hot water, I just want the practice corrected, hopefully through some training.