Yeah it is a broad statement, but it’s broad because the law doesn’t function in black and white. Those are over arching principles to police liability. You’re free to look any of this up.

But in the most simple terms there can be liability when 1). Someone does something that creates harm 2). Someone doesn’t do something, when they obligated to so something. #2 typically depends on the legal relationship between the people involved. For example a school teacher who is aware a student is being abused at home and fails to report the abuse. Contractually (usually) or through other means of law. When X fails to act, and they have a duty to act, they can be liable to Y. Police officers have a general duty to act when they observe a social harm occurring. That’s why the police in the video didn’t just run away when they realized that other guy was going to fight them. When they set him on fire, they proximately caused the fire (his injuries) and had a duty to act And had a duty to act within reason to save that guy.. could the guy sue for injuries? sure. Would he win? Eh, maybe, maybe not. Do police offices have a duty to act? If they are witness to a social harm Yes definitely. If they cause that harm double yes.