Honestly? I’d bet there are a lot more who get caught after their first then there are who get away with one and then decide never to do it again. Almost every serial killer I’ve ever read about has described the urge to kill as something that increases over time, and that is temporarily relieved by killing but comes back faster and harder after each kill. I suppose there’s natural selection bias against it, but I’ve never heard of anyone who killed once and then was satisfied.

Besides, anyone capable of thinking “I’d rather not get caught” after their first kill was capable of thinking that before their first kill too. I’m not saying it’s impossible as defined, but by it’s nature would be vanishingly rare.