Around San Francisco, the name "Zodiac" evokes darkness. Four decades have done nothing to diminish the brutality of his crimes -- five executions by bullet and blade -- or their hold on the popular imagination.
For two years in the late 1960s the Zodiac killed, taunting police in a string of letters, some encrypted, to local newspapers. Then he disappeared, leaving behind a bloody mystery that remains unsolved.
"It was scary, and the murders were real, and they were terrible -- totally innocent people killed for no reason by this psychopath," said Lance Williams, a journalist with the Berkeley-based Center for Investigative Reporting who wrote about the Zodiac crimes for the San Francisco Chronicle.
To this day, police and journalists receive tips on the murders. And there's a thriving cottage industry of enthusiastic amateur Zodiac sleuths, some of whom have devoted their lives to the mystery.
The Zodiac's first claimed murders were in Benicia, Calif., and nearby Vallejo. In both cases the killer pulled up next to a young couple parked in a car and shot them point-blank. Later he stabbed a couple picnicking at Lake Berryessa, in Napa County, and shot a cab driver in San Francisco. He often called police from pay phones to report his crimes.
"There was hysteria," said Matt Meredith, who grew up in Vallejo and now is a detective in charge of the Zodiac killing that took place in a park outside of town. "It altered people's lives."
After the San Francisco killing, the Zodiac sent a swatch of bloody cloth from the victim with a letter to the Chronicle.
"The Zodiac would write letters to the Chronicle, letters to the editor, bragging of his exploits," said Williams. "They often started by saying, 'This is the Zodiac speaking.'"
Hollywood was captivated. The 2007 film "Zodiac" spawned renewed interest in the murders and the murderer.
"Back when I was a kid, there was a rumor and talk that the Zodiac lived in a cave and don't go up in that cave," said Meredith. He produced a large police binder. "All the tips in this binder deal with the Zodiac case," he said. "But these are all tips that came in 2007."
That's when the movie came out and police had to establish a Web site for an avalanche of tips. Meredith still gets at least one a day.
"I see every tip," he said. "I read every tip. Some of them are ridiculous. Some of them are compelling, for lack of a better word, but I read every one."
Williams still gets tips too, every time he writes a story about the Zodiac. "There's a flurry of contacts from people all over the place who think they've solved it," he said. "They range from 17-year-old boys to retirees. We've heard from people from all over the world, not just in the Bay Area. ... It's San Francisco's all-time unsolved murder mystery, even though only one of the murders was actually in San Francisco."
Williams has kept many of the letters and e-mails. Some point to family members. "For many years now," reads one letter, "I have been researching the possibility that my husband of 20 years was indeed the killer." Other tipsters claim to have broken the killer's mysterious code. "I decoded one of his ciphers that reveals his full name," one tipster wrote.
And then there are the letters that recount close encounters with the killer. "I met the Zodiac inside a dark bar in California in 1974 and we talked face-to-face for three hours," reads one letter Williams received.