When that guy is shooting at you? Seriously, this fall under self-defense, fair and square.
Surely there was another way to handle a 107 year old man firing a handgun than to kill him? He only has so many bullets. I've heard that they threw a "distraction" device at him then killed him, but information is hazy at the moment, as you would imagine.
We don't know, but this man could have been suffering from dementia and was sundowning. In fact, he probably was at that age. We need to have better ways of dealing with guys like that than to just kill them. If my grandmother had a handgun and was only a bit more aggressive, I could see her pulling something like this when she gets bad.
I've often been interested in the protocols for "self defence" and killing people and so forth though. I understand that in a place like the USA where owning a gun for self defence is quite possible, people are advised to shoot to kill if they encounter a burglar in their house because it's the easiest way to deal with them. If they maim them in some way (at least, if the burglar survives), the burglar can sue you for a large sum of money and possibly have your gun taken away. Police officers seem to take the line that if there is any risk, euphemisms like "neutralise the threat" start getting thrown around and someone gets shot and killed. I know it's the most practical, safe way to deal with a guy with a gun after negotiations fail, but maybe this case will show that the practical, safe way isn't always the prettiest and can lead to
repugnant outcomes.