There are serial killers out there that make Ted Bundy and BTK look like Boy Scouts, they just haven’t been found yet and there’s a good chance they never will.
On that note, Jack the Ripper probably lived out his life and died a happy old man, and nobody at his funeral had any clue about the terrible and horrible things he did. Young children probably played in the street in front of his house as he sat in a rocking chair and waved to them.