Let me start out by saying that in my circle of people with whom I regularly train on the mat or at the range, 25-30% are cops. I whitewater with cops, go boating with cops, etc.
My cousin is a retired cop, for that matter.
I don't have anything against cops, as a group.
But this incident is really troubling. The thing that bothers me most is that the shooter LEFT THE SCENE.
I can't think of anything that justifies that. Period. Should have been calling dispatch immediately, via his cell phone (I don't know a cop who carries a gun, but not a phone at the same time off-duty) or the victim's phone. Should have been ensuring EMS was sent. Should have been doing any number of things that were not what he actually did.
While we still need more facts, initial impression of this one is very, very negative.