... I wish I would do the following: check wheter I had a very good chance to save the clerk from the threat, pull and aim very slowly and silent at the back or the side of the BGs head and then shoot well aimed untill the BG stops moving at all.
I also wish that I would only escalate things and open fire if my chances to end up holding the only gun fired were excellent.
I wish that I wouldn't end up regretting why I didn't save a shot clerk athough I could have - likewise - why I started a shooting that killed innocent bystanders ...
Maybe English isn't your native language; and something has been lost in translation; but, I got 'a tell ya, that's some of the worst advice I've ever heard!
It might have passed muster 100 years ago in the old West; but it's positively antique in 20th century America.
PS: Besides, what happens if you do shoot the BG in the back of the head, miss the pons, and the BG reflexes, pulls the trigger, and shoots the clerk as a result of your shot?
Please DO spend more time in these forums!