Need info on what someone would bring on nonofficial business.

Research about what a detective would do/bring in a certain event.

I'm developing a game. And in some aspects, I'd like it to be as realistic as possible.

Your main character is a detective at a unspecified precinct. A long lost friend reaches out to you. Something "fishy" is going on, and he would like you to come check it out.

It's unofficial business, but you trust your friend that something is going on.

I would like to have my character go to the location with his firearm, an extra clip. A flashlight and a small audio recorder. (Badge/ID?)

Question is: Is this realistic? Or what would you bring in such a case?

I don't live in the states, and all I know of the topic is from movies/media, which isn't saying a lot.

Anyway. Hope to get some answers / examples.

Otherwise, have a good day.