Nobody has the right to shoot someone else and infringe on the rights of another person. Cops don't either. There are specific laws and rules in our society that dictate which ways and situations are ok to violate the other person. Ie: they were choking you illegally or similar. You can disagree that this should be the case, but nevertheless, here we are. It isn't about rights. In many places you will go to jail for killing someone, unless you prove self defense. Same against a cop.
Reason has a good story on a recent case last year.
I haven't followed up however.