We teach in the classes in Texas that you always say if asked, "I shot to stop the threat". You never tell the authorities or anyone else that your intentions were to kill. Now if the BG happens to expire then so be it. As for shooting him as he flees if he just pulled off an armed car jacking I believe that is a felony and under Texas law you can shot to stop the fleeing subject.
By faith Noah,being warned of God of things not seen as yet, moved with fear,prepared an ark to the saving of his house;by the which he condemned the world,and became heir of the righteousness which is by faith Heb.11:7