DISCLAIMER: I don't own any of the characters; other, more important, people have that privilege. This is just a little headcanon of mine.
Sebastian Moran was on the staircases of one of the highest, yet most desolate building in London. His gun rested on the window sill and pointed outward. He'd not been there long before his target arrived. But he had to wait. The noise of the city faded in and out, sometimes replaced by maddening silence in his mind. It was during one of these moments of silence that he heard the shot. One bang amidst the roar of general life; it shook him. For a brief moment his brain was flooded: thoughts, fears, emotion. He shook his head sharply. Now was neither the time nor the place.
He regained his stature and positioned the sniper rifle. When he thought about it, sat here with Dr Watson in his crosshairs, he wasn't in an entirely unfamiliar situation. The memory of Afghanistan came back all too easily. Enemy fire in all directions and a doctor in the middle of it, doing his best to save a friend. This friend was never going to be saved, nor any other men that day. He was an easy target, especially for a man like colonel Moran. The shot was of mercy, it was never meant to kill, just maim or seriously injure. John Watson wasn't made for the army; he felt too much. The job was getting to him and for his own good (and to save his pride) Sebastian had taken matters into his own hands.
They never could prove that he was the one who fired. A through and through shot to the left shoulder. They told the good doctor it was enemy fire, but discharged the colonel all the same. After all, he had fired his weapon without due cause. He was under strict orders not to shoot unless directed to. Fairly similar to now, he pondered.
A few moments passed whilst he wondered if not shooting John the first time would've avoided having to shoot him a second, or prevented the death of his boss and all those others who lost out in the game played with Sherlock Holmes. He didn't need to shoot Watson a second time. He watched as the consulting detective fell gracefully to the pavement and landed. His target escaped in grief and panic and Sebastian lowered his weapon. They had both lost someone in this and, although they'd been discharged from the army, they would forever be fighting a war.
AN: Ridiculously short, I know, but I just felt like this was something to be published. Thanks for reading.