Beside I am not sure if a police officer is ever off duty. Especially if he is on his way to, or from work, and in uniform. But then I am not a policeman, just an average citizen with a common impression that the police has a certain amount of authority to enforce the peace.
Most cops I know make a point of not working when they are not at work, the same as anyone else.
I helped put my ex-BIL through the Police Academy.
IIRC once you are a sworn peace officer you are one 24x7x365. Even if you are "off duty" you still have to enforce the law. If you see a crime you have to attempt to stop it and apprehend the suspects. The difference is you don't go looking for crime when you are off duty.
And I also think they have to have their service weapons with or near them at all times.