I suspect the BG experienced tunnel vision
When people engage in violent acts, many times they experience tunnel vision to varying degrees, as would/will all of us should we ever have to draw defensively. Any police here have seen the literature. Most likely, the BG either was so focused on the woman, or alternately so drugged or tanked, that he probably never even saw the GG draw. So, my take on this is, the man did precisely what I practice in hopes of never having to do. God bless the GG and may God take pity of the BG's soul, because the poor SOB surely won't find any pity here on THR!
Doc2005