Decided to weigh in on this thread because I have something to offer from experience. In Nam as a combat photographer I mostly shot a camera. Only when things got bad did the “Every Marine is a rifleman” kick in. My experience was that when you are under fire and returning fire, especially at close quarters, you absolutely lose awareness of all except the aggressor(s) you are engaged with. It is due to a combination of training and instinct. I can assure you that I such a situation you are driven be self-preservation. So, you are totally focused on staying alive. That means you are totally focused in the enemy. Even when the shooting stops you stay so focused for a short time because you want to be sure it over before you let down. While in that hyper state you might not even hear the mane next to calling your name. Your awareness is directed at the possible continuing threat. So, I can understand not obeying a command to drop a weapon while under fire or moments thereafter. This time it sucks.
Thanks for sharing from personal experience. Good training will incorporate a search and breathe scan after engaging a target to get oxygen back to the brain and reacquire situational awareness.