Only done one law paper, for non American law however a few things stand out. Sorry I don't have the cases on hand (I can look them up if anyone can give me the case name and where it was published).

"Duty to Uphold law, not protect people." This makes sense. The job of the police is to uphold the law, not protect people unless a person coming into harm is doing so because a person is not following the law. As an example, it's not the job of the police to protect a person who is going to kill themselves from alcoholism as drinking is not illegal - only actions taken while drinking.

"Protect people from harm". Similar to above but this seems to be along the lines of how people can be harmed while police are upholding the law - think of a person who steals a car getting injured when the police run them off the road. That person was harmed in the action of upholding the law.

"Protect students". I assume this was a school shooting... because Americans. The police job is to stop the shooter as soon as possible to prevent further harm, not protect the people the shooter is trying to kill. Can't remember the name - that recent one where the police stood around a corner being useless? They could have argued that they were protecting other students, however this was not their job (cowards). Their job was to stop the shooter - and the training stated their role was to engage the shooter asap and with everything they had - not Protect people behind them.

Saying all of this, I can guarantee these decions have been manipulated to avoid responsibility.