Write a story that seems normal on first sight , except for one small detail that makes it extremely creepy on a more careful reading [ WP ]

Time travel was always tricky business. It was never straightforward, and the results never predictable. The year was 1907, and the location was Vienna, Austria. It was a cool spring morning as I ruffled the collar on my favorite faded leather jacket and glanced out the window. It was the same, every single time I visited this timeframe. That's another thing about time travel - you'd think you'd get used to it, how everything is exactly the same. And in a sense, it does make things feel more... artificial, in a way. But this was not a fevered dream, or an idle fantasy. This was real, as was what was about to happen. 
 
 A serious and brooding young man stormed out of the institute of art, swarthy hair unkempt and small mustache barely existing. He looked angry. But then again, anger had always been that man's hallmark. It was that unrelenting rage, that burning fury that caused him to become the monster he would one day be remembered for. I took the small pistol out of the pocket of my coat. It was the wrong shape, the wrong size, and far too advanced for this era, but that would not matter. 
 
 I aim the pistol, being very careful to steady my hand to prevent it from shaking. I squeeze the trigger, and a soft report answers. Modern technology certainly was quite impressive, to mask the sound of such a powerful shot. The bullet sailed across the vast distance from my hotel room, through the chilly Vienna air, striking its target with unerring precision. A young man falls to the ground, senseless. The man who walked out of the building whirled around, but from all appearances it seemed that a random stranger had collapsed. He continues to stalk away, mumbling half-audible curses in German as he left. 
 
 Time travel is a tricky business. I've seen what happens when certain events are changed. How many times have I come here, done this? I have lost count. Sometimes I wonder if this is to be my fate: an eternal guardian to a man I loathed. Time, it seems, has a cruel sense of humor. 
 
 I light a cigarette and stare morosely at the man I shot. A man in a faded leather jacket.
