There is virtually no difference between on-duty and off-duty. Off-duty is arranged through the police department. This is the Minneapolis PD’s code of conduct for off-duty police officers:

They can’t just walk off the job. Here is the Minneapolis Police departments code of conduct for OFF-DUTY jobs! It says, in very small part, “Minneapolis Police Department employees who work off-duty are subject to the rules, regulations, ordinances, and the policies and procedures of the City of Minneapolis and…

Actually, many off-duty jobs require that police officers wear their uniform to that job. Don’t know whether this was one. The officers are still held to the requirements, standards and oaths of their profession, regardless of whether they are wearing their uniform at an off-duty job, because they are armed and acting…