I would think a shot through the thoat, or upper chest would be a more effective shot especially if it hits the spine, or the spinal cord would give you a better chance at dropping the bg. Most Spinal shots are deadly which will stop the attack in 10 out of 10 cases.
If he is still moving forward a shot to the knee will stop his forward progress.
This is just my opinion
"God created Man; Sam Colt made them all equal."