When someone expressly threatens your safety, you have the moral right to kill them

I'm not talking strictly self-defense, but a similar vein. I heard a news story recently where somebody broke into a house, the owner came home, chased the burgalar and shot them dead. The guy is being tried for murder, because the burgalar fled, they weren't directly protecting themself

In my opinion, when you break into someone elses home, you no longer have rights, there is no arguing for your own "self-defense". You've chosen to exit civilized society, now you're following the laws of the jungle. The guy had no obligation to show mercy to the burgalar, and give them the opportunity to return someday