Well, it's a common misconception that most serial killers are insane.
However, more often than not, they are consummate chameleons.
They're able to hide their rage and their true intentions behind a more civilized fa?ade, what we refer to as mask of sanity.
Likely hiding in plain sight scouting the victims.
They kill their victims in one location, and then dispose of them in another, like Deacon MacKenna, The Trashman.