Sometimes shootings are not good or bad, just a tragic mess.
With regards to the freedom of opening your door holding a pistol, that may be so, but deconfliction is a critical tactics element.
Having worked old clothes as a police officer, I can assure you that identification of friend/foe can be difficult.
Not all police shootings are bad.....
I can assure you that the involved officer is a mess and facing months if not years of investigatory stuff as well as a lifetime of doubts.
Let me add a military perspective on this, since we also train heavily on this.
If freind/foe identification is giving you trouble, DON'T *expletive deleted*ing SHOOT!
What is so *expletive deleted*ing hard about the basic tenant of fire arm use: "Obtain positive target ID before firing"?
The police officer did not have positive ID of a threat, and fired prematurely.
Honestly the real problem here is that police officers have forgotten, and convinced us to forget, that their job might entail taking incoming fire before they are justified in returning it. Sucks, but that's the gig.
ETA:
Cordex was actually pretty accurate in post 18:
The cop sees someone moving around in the house with a firearm when the homeowner was reportedly unreachable and had ostensibly activated a silent panic alarm. At that time he reasonably believed the person he saw turning around with a gun might be an active threat.
I'd agree with that. Guy might be a threat. Cops shouldn't shoot at "might be a threat". It's their job to ascertain threat vs. Not threat before firing. Or it should be.