I wonder if people who have received military training or have been deployed into a war zone where they have had to fire their weapon at an enemy are better able to pull the trigger without hesitation or second thought than someone like me who has no formal training.
I can't speak for every soldier or military unit, but when I was in the USAF, during my training at the Security Police Academy you were taught to look for 3 preconditions, if met then shoot, we used a system called "FATS" (Fire Arms Training Simulator) that put us into shoot/don't shoot scenarios, by the time all was said and done you didn't even think about it, it became instinct once the preconditions were met.
As for in combat, there's even less thinking, you're trained to react and make quick assessments of the situation and act to stop the threat.
That was the long answer, the short answer...
Yes, you pull without hesitation because you understand that it isn't the movies, there is no retake, it's his life or yours and your fellow soldiers, and they're your family, so there's no thinking or consideration in the matter.