Grand theft auto in itself does not inherently include force or violence, without looking up more specific AR law for you, in many states it can be felony or misdemeanor.
You're overlooking parts of the law, such as the duty to retreat and the use of force or violence. Yes in your example violence was used, but in your example, the violence was over, then deadly force was employed to stop a fleeing BG, and again...how do you explain that you could not safely retreat from that situation?
Furthermore, you have yet to cite statute or case law that supports your opinion. Where are the statutes and/or case law that support deadly force after the fact? Or warning shots? Or shooting out car tires?