The difference is a random citizen shooting you will go to jail if they get caught. A police officer will get paid leave with a presumption that you did something to cause it while it is "investigated" by their brothers/sisters in blue.
If their brothers/sisters in blue don't like them then they will be arrested for murder if they acted inappropriately.
Otherwise the investigation will likely be half-assed or purposely sabotaged. The "blue line" is a real thing, most cops won't take down other cops unless they have to/dislike the other cop.
