Should my life be under imminent deadly threat I shoot to stop the threat. The BG had better surrender real fast, because my gun is out and fired in 4 tenths of a second.
In the incident outlined, the robber did not present a weapon or rush the GG.
Why would I shoot an unarmed man 15 to 21 feet away from me? Because he says he has a weapon? Gotta do more than that. I would order him to stop and kiss the pavement, then call in the cavalry, and you wanna know I wouldn't take my eyes off the BG excepting glances to my six.