I've never heard anyone ask about a candidate being comfortable shooting firearms. Maybe some do, but I've never heard it asked myself.
What I have heard asked at each and every hiring board, is a question about my capability to take someone else's life. That may include a firearm, or a rock, or a squad car. They're more concerned with the candidate having a pre-determined moral point which allows them to kill another human being if required. Some questions were straight-forward and asked if I could take the life of another in the line of duty. Others were scenario-based where the only correct answer was to use lethal force on the offender.
Worry about the above more than firing a gun. You can be trained to handle a firearm rather proficiently in a short amount of time. If you are unwilling to killing someone when the situation calls for it, there's no need for them to continue the hiring process with you.
Of every one hundred men, ten should not even be here. Eighty are nothing but targets. Nine are real fighters, and we are lucky to have them, for they make the battle. Ah, but the One... One of them is a Warrior... He will bring the others back.
"Wrong door, buddy!"
Let no man's ghost say my training failed him.