Those of you arguing whether or not BG is still a threat in this scenario: good on you. BUT...you are missing the point of the thread. It wasn't about threat assessment, it was about leading, or identifying a need to lead. The question was mathematical in nature, not legal. Let's just assume for the sake of argument that since the situation is hypothetical that we're going to shoot said BG... let's not 'what-if' it to death, ok?
The compliance gods are happy, someone has posted the obligatory Legal Warning.
Now, let's just talk about whether or not to lead the moving target.