The Killer
It was night. It would have been fitting for it to have been a famously described "dark and stormy night", but that would have ruined the killer's plans. No, it's best when it's clear and quiet out. A bit of cloud cover, to block the light of the moon and stars, but no rain. No one is outside at night when it rains, remember.
The killer waits. A surprising amount of a serial killer's time is spent waiting. Waiting for the right victim. Waiting in the shadows. You've got to be patient. Yes, it's tedious to lurk out in the dark, when it's cold and damp outside and it's tempting to rush the job just for the sake of getting home to a warm fire. But you've got to be patient. It's always the arrogant ones that make a stupid mistake and get caught.
No accomplices, no witnesses.
After that it's almost frighteningly easy, or at least frightening to the victim, perhaps. The killer doesn't get scared, not of anything, not ever. But easy, yes. Very easy. People never think it'll be them, do they? It's always someone else, there's always the frankly idiotic idea that nothing bad can happen to oneself.
Take the right person at the right time, make sure to leave no traces behind, of a body or of yourself. The perfect murder leaves nothing behind at all. Simple, really: no body, no murder and no murder investigation. No suspects, no detectives. No one getting in the way of you and your perfect control. Just someone who went out for a walk one night and disappeared.
Wait. Observe. Don't get cocky, don't get over-confident. It's easy to think of the city as yours when you've removed a fair number of its people from existence, but the thing to do is own the city quietly. Stay in the shadows. Don't seek attention, don't take credit. You're clever, we know that, the world doesn't need to. Follow the rules, quick and quiet, don't get caught.
Hide in the shadows, wait, then strike.