Letter of Rec. for future University application
Your letters should preferably be written by one of your professors, that will hopefully be aware of the protocols on how to write them. Also, usually you don't get access to your letters, but provide the university you are applying to with the contact of recommendation writers that have agreed to write your letter. The idea is that letters are supposed to be blind, so the recommender can freely express their opinions about you, and also make sure you haven't tampered with it.

I would advise against getting a letter from the police chief. He can certify that you did that job (and that should be attached to your application), but he doesn't have the technical skills to evaluate your job beyond "it works", and he cannot put you in perspective compared with other students. Plus, industry letters are usually a string of cold facts:


  This person worked here from November to April developing the system C.


Whereas an academic letter is on the line of:


  I strongly recommend the student for the program because... as he showed working on ...
  [And some paragraphs more saying how awesome you are].