“...both the officer and the shooter made mistakes...”
What mistake did the shooter make? The shooter had NO duty to announce anything. The LEO was entering into the house.
In retro, I agree with you!
The “generic” mistake he made was that nearly ALL agree that you don’t pull a trigger on a loaded gun until you are absolutely, positively, 1,000% sure of what you are aiming at.
Now, as I said, the cops made mistakes too. The shooter is LUCKY that he wasn’t the one that is dead. I guess.