What I know is that when I asked years ago about the rules when it is allowed to use a weapon, that I was told, that in most cases it ends bad for the defender, because courts accept the use of fireweapons as justified in rare situations.
So shooting at burglar or somebody attacking you without a gun will cause you major troubles if the attacker should die.
It's just heavily discouraged here to solve any problem by aggression. Even for slapping or insulting someone publicly you'll be held accountable for that in court.
IANAL, and it varies by jurisdiction, but I believe the general standard for using deadly force is ..
'Not allowed to use deadly force against any person except as necessary in self-defense or the defense of another when they have reason to believe they or another are in danger of death or grievous bodily harm'
Paraphrasing from memory.
In other words, I can employ deadly force against an attacker if I believe he could kill me. Doesn't matter if he's armed with a club, a knife, or a bazooka.
I can't shoot a guy if he's running away.
This seems prudent, but that (he smiled) might be a cultural thing.
Where I grew up they used to say 'God made man, Sam Colt made them equal' and I guess I still believe it.
I do wonder where you got that idea, though. You can post the document, I speak German.