In the 30+ years I have lived in my home, I have only had someone knock on the door in the middle of the night once.
I retrieved my .38, opened a 2nd story window, and keeping the gun behind me, asked who it was. A man's voice answered that he had an accident and could he use my phone to call the police.
I told him to return to his car and that I would call the police for him.
I called the police, put my gun away, and went back to sleep. End of story.
That was the second time I had reached for a gun with the possibility that I might have to use it. The first time, I was in the Navy, after taps, standing guard over a nuclear weapon's magazine.
Technicians working on the ship's alarm system accidentally activated the nuclear security alarm. I suspected that it was a false alarm, but followed standard procedure by chambering a round in my .45 and looking around the deck for any intruders. Standard procedure also called for anyone not on the security force to step out of the flow of traffic and stay put.
A man in civilian clothes, whom I did not recognize, appeared and walked across the worst area he could be in at the worst possible time to be there. I ordered him to halt, then to keep his hands away from his sides and walk to a light about 20 feet ahead of him, then to lean forward and place his hands against the bulkhead (wall in Navy speak). I kept my finger off the trigger, and the muzzle pointed straight up, but watched him, like a hawk. Once he was under the light, I asked him where he kept his identification. He told me it was in his wallet in his left rear pants pocket. I told him not to move anything but his left hand and to produce his ID. When he flipped open his wallet and revealed his military ID, it turned out that he was a Marine Lt. Colonel temporarily assigned to the ship, and no one had given him a security brief when he checked aboard. I said he he could relax, but kept him at my station for his safety. Then explained what he should have done when the alarm sounded.
In both cases, an innocent party could have been a threat, and I took precautions to protect myself and my family or shipmates. In the case at my home, I was within my house and felt relatively secure. Aboard the ship, it was a completely different situation and, I'll admit, my pulse was racing. However, I never placed the suspected parties in any danger, but maintained the option to do so if necessary.
As one poster said earlier, deadly force should be the last resort.
All of the above was to make the point that I speak from experience. My take on the incident is:
To call this killing murder is evidence that the poster is more interested in pushing his political agenda than he is in speaking the truth. There was no malice or premeditation. This was an accident, one that might be considered manslaughter, but not murder.
Did the shooter have the right to go outside armed to investigate? Yes, however, it was stupid of him to do so, especially since the police were on the way.
Can an old man with Alzheimer's sound and look threatening in the dark? As one who frequently visits my father in a nursing home filled with such people, I know how loud and abusive people who suffer from the disease can be. If I were alone and in the dark, looking for someone who had been trying to get into my house, and encountered such a person, would I be scared? You bet I would!