Every municipality has different rules for officer's conduct. According to the Bureau of Justice Statistics (Part of the Federal US Department of Justice), there are 17,985 US police agencies, of which 15,400 departments govern the 39,044 distinct local governments and municipalities. These are further divided into autonomous administrative districts often referred to as precincts.
The rules for officer misconduct change in each municipality as reactions to prior conduct or complaints. The rules are based on edicts from the state, as well as interpretations of those edicts by the local police department which create internal policy. The level of compliance with creating and updating internal policies varies. No civilian is able to know or predict the various rationale an officer may use or is able to use to behave any particular way. Civilians learn after they have had a bad encounter with an officer, or are in jail or dead. Juries learn on the spot with prosecutor instructions, sometimes those instructions themselves are misleading or incorrect. The public does not necessarily ever learn what the standards were, and the media learns after the fact and only has a patchwork of "isolated incidents" that occurred in frankly different governing systems. When put together, this fuels discontent with police as an amorphous entity, an interpretation which fuels a growing divide of non-solutions.
So the term "justified" and "unjustified" means nothing because it is different and changing everywhere and is a term that only matches your pre-existing worldview, or your predilection to appeal to authority in counties and states you have never set foot in, let alone participate in.
Germany has 16 state level and one federal, plus customs (not legally a police force with a lot less jurisdiction)
France has two, Police national and Gendamerie.
Obviously a slight oversimplification when counting stuff like the BKA / LKA (maybe the German equivalent to the FBI?) as seperate bodies. But roughly across Europe you have two levels,local and federal. Both are reporting, one way or the other, to the respective Ministeries of the Interior. Quite adifference compared to the US, where the highest authority can be a mayor. or none, if I understood the thing with local Sherrifs correctly.