They're either murderous or have "lucky" bad aim.
Exceptions apply for swat snipers in hostage situation
Which is the whole point of the protests. If an officer is on a riot line and is murderous but the other officers on the line don't take them out (send them home or prosecute them), then the officers are just selectively enforcing the law (which I realize is a concept in US law enforcement) to the point of being corrupt.