By contrast, if a police officer kills a citizen in the line of duty, their actions are considered legitimate until investigation proves otherwise. While their weapon may be taken for lab testing, a sympathetic fellow officer will be quick to offer a backup weapon. The investigation on them will take a known format, allotting a certain amount of time on immediate leave and making a statement at a known later time. And every investigator looking into the officer's case will be knowledgeable of what it is to wear a badge and not know if they will return home that night.
That an officer's oath calls them to run towards the sound of the gunfire is a shield that only covers so much, and has been cracking for years under the beatings of public opinion. Ignorant though that opinion may be of the particulars, they know the scent of "rule for thee but not for me," and have been increasingly unwilling to abide such a thing.