I wrote this as a quick exercise, and I intend for it to be the start of a chain story that other users here can submit to. Feel free to pickup where others leave off, and let's see where this story goes!
There it was again. It was always the same, no matter how long it had been. It was a smell, but more than a smell. It was a sharp sensation, quick to approach and then dead before the breath was finished. Tommy knew it was the smell of change. Something was about to happen, but there was no way to know what or when. It made him nervous as he shuffled across the cobblestone road, fists clenched tightly in his coat pockets. He did not dare take his eyes off the ground lest his feet catch on a loose rock or crash into one of the myriad puddles that were now forming. Despite how occupied his gaze was, necessity forced him to cast furtive glances at the passersby around him. It could be any one of them, and he was not going to make the same mistake as last time.
Then it hits him. It's not the people around him. It's the people around his reflection in the puddles. There was a flash of a knife and an arm around his throat. The man next to him clutched at his chest but there was no attacker on this side, no knife, and no blood. It looked like the man was having a heart attack.
Tommy was about to slink away but stopped himself. If he ran it might cause the attackers to single him out. He stood still and stared at the dying man, scrupulously averting his eyes from the water he was lying in.
EDIT: added "man next to him". EXCUSE: It's a first draft.