When someone is shooting at you at very close range, you don't have the ability to make a conscious choice. That part of your brain is out of operation at that moment.
Exactly, the adrenal gland would go into overtime and there's nothing any of us could do about it. I still contend that not a single one of us knows for sure exactly what we would do or be capable of doing in a similar situation.
Just the fact (if it is a fact) that he drew his weapon and returned fire, is fairly impressive in and of itself.