Years ago I went down the mother of all rabbit holes, The Zodiac Killer case. It's frustrating that a guy who was seen, left survivors and wrote numerous letters about his crimes has never been caught. There are the four "known" attacks, but many believe he was responsible for many more over many years. Just recently a very Zodiac like murder was uncovered that happened near San Diego in 1962. He killed a Taxi driver, made calls to the police and threatened to shoot up a bus. There are other very similar killings in Southern California before the San Francisco bay area attacks.
Anyone interested in the case, if you have never seen this, possibly the best crime documentary ever made, in my opinion. It's was done back in 2007 by the same people who did the Zodiac movie. You'll get to hear from many of the police officers involved and also the two surviving victims. All I can say about victim Michael Mageau is, holy crap!, You'll understand if you watch the documentary.