Because if he turned to flee then you still can't shoot. you have to feel directly threatened.
They can also tell a lot about trajectory and distance etc.
maybe, but what if he was turning around so he could pull out his gun slightly hidden to give himself an advantage. What if he turned around to call his mate to come and help him.
Turning around does not somehow equate to complete and utter safety., Especially in his case as they had robbed him repeatedly(if its the case I'm thinking of) so he would have still been under the impression they would be back, next time knowing he had a weapon they'd be more likely to come back armed which means he was still protecting himself.
Frankly I'm happy to see anyone commiting a crime behind hurt/killed during it I just don't care.
Literally I don't care in any amount of people willing to commit horrible crimes are removed from our world.
This crap of its only burglary, how the hell do you know that in any given burglary the person isn't either intending to harm someone in the house specifically, or went in the with full intention of hurting anyone that got in his way. The intent is assault or worse. Just because someone "only" took a few items in no way whatsoever means he wasn't intending to do much worse.
Who decides to rob a house and doesn't remotely concider who might be inside or what they might do should someone find them. How many people capable of burglary do you think have that run through their mind and don't decide harming others to protect themselves(protect themselves physically and protect themselves from being caught, as in, a guy says he'll call the police if they don't go, he decides to kill him to stop the police coming rather than just for the sake of killing someone). I would hazard a guess that the majority of people willing to break in our willing to commit an assault to get away also.
Where this idea comes from that theres a bunch of really nice robber's out there who would run away at the mere asking by a homeowner and would never dream of doing anything violent, I don't know, people are just stupid/naive.
You don't have to actually kill someone to be found guilty of attempted murder, in the case of most robberies for me a lack of assault is lucky, the general idea for most robbers is if someone tries to stop you, you stop them. From there, they deserve what they get.