True, thought the shooter would have several things to explain, most likely to a criminal court... Why were you carrying said weapon? Why was it loaded? Why did you confront this person? What other options did you consider? How could you have possibly known so much about this person's ability and intent to use lethal force against you, using your own weapon? Are you lawfully allowed to carry loaded firearms? If you knew so much, why did you put yourself in this situation in the first place? And so on. People have shot and killed other people in Australia and not been charged with an unlawful killing offence, but it's an exception to the rule. A self-defence argument is always going to be examined in minute detail in the case of what otherwise, would be a homicide (even if it is only manslaughter through diminished criminal responsibility).