December 20 mark’s the 50th anniversary of the Zodiac’s first known murder, and several dozen die-hard aficionados planned a “bus tour” to remember the occasion. However, a man some think is dangerously delusional has threatened to kill anyone who shows up on the desolate Lake Herman Road site on the anniversary, so the trip is canceled, its organizer said.

Zodiac obsessive and author, Mark Hewitt of Santa Rosa, plans to mark the event at some point, anyway, he said.

“Solano County has reports of a murder threat surrounding the event, but I’m planning to be (there,). I know others who will not be due to the threat,” he said, placing his faith in the belief that “people who make threats like this, rarely carry them out.”

Another longtime Zodiac obsessive, Tom Voight, who maintains a website on the case, planned the bus tour, but canceled it and refunded people’s money, Hewitt said.

Hewitt said he got an email alerting him to the change of plans: “Mark I have some bad news about Lake Herman Road, please let Ricardo know. Solano County Sheriffs department was told that (a Santa Rosa man), who wants to kill Ricardo and I, has threatened to kill everyone at Lake Herman Road on Dec 20th!,” the email says. “Tom just sent me an email to refund the money to everyone. I know this guy is very dangerous and was being treated for mental illness. Please pass this on to the rest of our group. Thanks.”

No one from the Solano County Sheriff’s Office returned calls for comment.

Voight said he’d planned an event similar to one he hosted for the 40th anniversary of the slayings, but the threat posed by the man was enough to warn him off.

“He’s a mental patient with a history of stalking us at past Zodiac gatherings, and making terroristic threats,” he said. “I’d never heard of him, but he started contacting me at least a month ago on Facebook.”

Another member of the Bay Area Zodiac group, Sandy Betts, said she’s been the target of death threats from this same person. She said she thinks he poses enough of a threat to keep her away on the anniversary, as well.

“I am scared to death to go,” she said. “I contacted the FBI about the threat of this guy who threatened to kill us all if we showed up there. The Solano County Sheriff’s office said they didn’t think it would be safe for us to go there.”

Saying she’s met the man and describes him as “a nut,” Betts agreed with the other two “targets” that “he thinks his father is the Zodiac and that we are all part of a Satanic cult trying to kill him.”

Voight and Betts said their contacts with the man were escalating from Facebook posts to threatening phone calls and personal emails.

“He believes his father is the Zodiac and tried to kill him and went to prison for it,” Voight said. “He believes everyone who doesn’t believe what he does is part of a pedophile ring. He warned everyone not to go near Lake Herman Road on that date, and I couldn’t risk continuing with the event.”

Some of the targets of the threats said they notified the Federal Bureau of Investigation.

“I can confirm that the FBI San Francisco received a public tip regarding an upcoming gathering in Solano County and promptly disseminated the information to the Solano County Sheriff’s Department,” San Francisco FBI agent Cameron Rogers Polan said in an email. “An accurate threat assessment would need to come from the Solano County Sheriff’s office as it is their jurisdiction. Our office felt it a priority to pass along the information to the SCSO, but did not involve the FBI Sacramento Division (Solano County is Sacramento’s territory.)”

Voight said he had about 30 people already signed up for the tour when he canceled it, and figured the bus would have been fully booked, with about 60 people, had it gone forward.

“I was going to have security and all that, but if someone is hiding behind a tree determined to do damage…,” he said. “There’s a big difference between someone making threats and someone who poses a threat. He poses a threat, and I don’t want to press my luck. I’ve been 22 years dealing with zodiac stuff and I don’t spook easily, but this is a bad one, and there are four more 50th anniversaries next year.”

One tweet allegedly from the threatening man, says, “they need to arrest tom voigt (sic) and all the exploiters stonewalling and antagonizing me for survivng(sic) organized pedophelia(sic) related to the zodiac cases. tom is got to burn eternally in hell for provoking and stalking me and my peers.”

Betts said she plans to mark the occasion as best she can without taking the risk.

“He’s threatened me and many other people, and I’m hoping they arrest him,” she said. “It’s a shame. We had plans. I made two crosses – for Betty Lou (Jenson) and David (Faraday) – and decorated them, and wanted to take them out to the site. They will be put up one way or another.”