I’m going to play devil’s advocate here: how is the guy on the phone supposed to know it really is the police on the other side and not just some guy trying to scam his way into a freebie?
At the individual level this is actually pretty simple. I work in IT and when I used to do security training the way we’d validate is with a known contact.
In this situation you get the contacting officers name and department, disconnect the call, call the non-emergency listed number for that department and ask for that officer by name.
There’s a lot of other failure point potential in this scenario but validating the person calling is actually law enforcement shouldn’t be one of them.