As a police officer, my schedule changes every week. If I am ordered to work Friday night or Saturday during the day, can I work? My work consists of driving a police vehicle. I write tickets and reports. Arrest men and women. Use and carry radio, weapon, flashlight, handcuffs and pen. In addition, what if I am ordered to desk duty, where I am not saving lives. How does that affect Shabbat?
Your question is a very complex one and needs direct guidance form a rabbi that knows you and the nature of your work. I will try to bring a few points in general terms that shed a bit of light on this topic based on the writings of Rav Waldinberg [Tzitz Eliezer 4; 4] Rav Yisraeli [Amud Hymini 17] and Tchumin  The work of the police to maintain normal peaceful life of citizens by patrolling and attending cases of conflict is considered to stand within the category of life saving duties that can override Shabbat laws. In any case where it is possible to avoid breaking Shabbat it should be done. A non-Jewish policeman should drive when possible, recordings should be made when writing can wait till the end of Shabbat, arresting should be avoided if not necessary for the public's safety. Similarly, work that has nothing of the nature that can protect and save lives of citizens, should be done after the Shabbat. As I mentioned, these are general rules, the details should be discussed with a rabbi who knows the details in depth.