It seems like it came into his mind as he listed all these things that were potential problems and might get him caught... UNLESS... unless there were things he could do to MISLEAD them on to a different investigative path, leading anywhere but to him. And he obviously thinks he's this super-genius, smarter than all LE anyway, and he may have started thinking he could basically tell them what or how to think, just by purposefully leaving them clues that were really anti- clues! So that he could claw back some of that control that he always felt he had to have in any situation IMO. Committing such barbaric and wild, crazy acts had to necessarily involve giving up some control over the situation, since things never go exactly as planned or the way he'd like them to, since his prey was HUMANS, known to be unpredictable, to put it mildly. Identifying and employing some clever (to him) misleading items or actions, etc. could give him back some of that lost control, allowing him to steer the investigation away from himself