Story highlights One of two Zodiac Killer survivors says someone always stirs up the unsolved case

Gary L. Stewart was abandoned as a baby in a stairwell in a Louisiana tenement

He claims his late biological father, Earl Van Best Jr., was the Zodiac Killer

Investigators say they aren't aware of the book but will look into its claims

A Louisiana man claims in a new book that his biological father was the notorious Zodiac Killer of northern California, who's still sought by authorities, publisher HarperCollins said Tuesday.

The Zodiac serial killer is believed to have killed five people in 1968-69 and gained notoriety by writing several letters to police boasting of the slayings, with swatches of bloody clothing as proof of his claims. The serial killer claimed to have killed as many as 37 people and has never been caught.

Now Gary L. Stewart, a vice president at the cleaning company Delta Tech Service in Baton Rouge, is recounting his decade-long search for his biological father and has concluded that man -- Earl Van Best, Jr., who's now dead -- was the Zodiac Killer, the publisher said.

On Tuesday, police in northern California said they weren't aware of the book or its claims.

"It's an open and active case, so we don't comment," San Francisco police spokesman Albie Esparza told CNN. "But (it's) certainly something our homicide investigators will take a look at."

A Louisiana man claims his father, Earl Van Best, Jr., who's now dead -- was the Zodiac Killer.

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Added Capt. Steve Blower of the Napa County Sheriff's Office: "We have talked to many people over the years. We've gotten reports over the years from people who don't pan out. This case is still open, and we still do accept tips or leads that may have bearing on the case."

Bryan Hartnell, one of only two survivors of the Zodiac Killer, was just a college kid more than 40 years ago at Pacific Union College, just north of San Francisco, when he and a then-girlfriend, Cecilia Shephard, were attacked while picnicking. Their attacker was a man in an eerie costume: he wore a black hood and black shirt with a white symbol on the front that looked like crosshairs on a gun sight. That image would later become the Zodiac's trademark symbol.

On Tuesday, Hartnell expressed reservations about the latest claim in the unsolved case.

Photos: Infamous serial killers Photos: Infamous serial killers John Wayne Gacy killed 33 men and boys between 1972 and 1978. Many of his victims, mostly drifters and runaways, were buried in a crawlspace beneath his suburban Chicago home. Here's a look at some other notorious convicted serial killers. Hide Caption 1 of 26 Photos: Infamous serial killers Jeffery Dahmer was sentenced to 15 consecutive life terms for the murders of 17 men and boys in the Milwaukee area between 1978 and 1991. Dahmer had sex with the corpses of his victims and kept the body parts of others, some of which he ate. Dahmer and another prison inmate were beaten to death during a work detail in November 1994. Hide Caption 2 of 26 Photos: Infamous serial killers Law enforcement officers meet in San Francisco in 1969 to compare notes on the Zodiac Killer, who is believed to have killed five people in 1968 and 1969. The killer gained notoriety by writing several letters to police boasting of the slayings. He claimed to have killed as many as 37 people and has never been caught. Hide Caption 3 of 26 Photos: Infamous serial killers Authorities said DNA recovered from the body of Mary Sullivan matches that of her suspected killer, the confessed Boston Strangler, Albert DeSalvo. After a sample was secretly collected from a relative, DeSalvo's body was exhumed in July 2013 for more DNA testing. From mid-1962 to early 1964, the Boston Strangler killed at least 13 women. DeSalvo was stabbed to death in 1973 while serving a prison sentence for rape. Hide Caption 4 of 26 Photos: Infamous serial killers Ed Gein killed at least two women and dug up the corpses of several others from a cemetery in Wisconsin, using their skin and body parts to make clothing and household objects in the 1950s. Hide Caption 5 of 26 Photos: Infamous serial killers In 1973, Juan Corona, a California farm laborer, was sentenced to 25 consecutive life sentences for the murders of 25 people found hacked to death in shallow graves. Hide Caption 6 of 26 Photos: Infamous serial killers Joseph Paul Franklin was convicted in 1997 of murdering Gerald Gordon outside a St. Louis synagogue in 1977. Franklin was also convicted of at least five other murders, receiving a string of life sentences, but he suggested that he was responsible for 22 murders. He was best known for shooting Hustler publisher Larry Flynt, who was paralyzed from the attack. Franklin was executed in November 2013. Hide Caption 7 of 26 Photos: Infamous serial killers In 1977, David Berkowitz, also known as Son of Sam, confessed to the murders of six people in New York City. Berkowitz, now serving six consecutive 25-to-life sentences, claimed that a demon spoke to him through a neighbor's dog. Hide Caption 8 of 26 Photos: Infamous serial killers Cousins Kenneth Bianchi, seen here, and Angelo Buono were charged with the murders of nine women between 1977 and 1978. Also known as the Hillside Stranglers, the cousins sexually assaulted and sometimes tortured their victims, leaving their bodies on roadsides in the hills of Southern California. Hide Caption 9 of 26 Photos: Infamous serial killers Wayne Williams killed at least two men between 1979 and 1981, and police believed he might have been responsible for more than 20 other deaths in the Atlanta area. Williams was convicted and sentenced to two life terms in 1982. Hide Caption 10 of 26 Photos: Infamous serial killers After serving 15 years for murdering his mother, Henry Lee Lucas was convicted in 1985 in nine more murders. Lucas was the only inmate spared from execution by Texas Gov. George W. Bush. Hide Caption 11 of 26 Photos: Infamous serial killers Richard Ramirez, also known as the Night Stalker, was convicted of 13 murders and sentenced to death in California in 1989. The self-proclaimed devil worshiper found his victims in quiet neighborhoods and entered their homes through unlocked windows and doors. Hide Caption 12 of 26 Photos: Infamous serial killers During a routine traffic stop, a police officer found a dead U.S. Marine in the front seat of a car driven by Randy Steven Kraft. Kraft was linked to 45 murders and sentenced to death in 1989. He would pick up hitchhikers, give them drugs and alcohol, sexually assault them and then mutilate and strangle them. Hide Caption 13 of 26 Photos: Infamous serial killers Ted Bundy raped and killed at least 16 young women in the early to mid-1970s before he was executed in 1989. A crowd of several hundred gathered outside the prison where he was executed, and they cheered at the news of his death. Hide Caption 14 of 26 Photos: Infamous serial killers Joel David Rifkin was stopped by police for driving without a license plate when a body was found in his pickup. Rifkin killed 17 women in New York between 1991 and 1993 and was sentenced to life in prison. Hide Caption 15 of 26 Photos: Infamous serial killers Charles Ng, seen here, and accomplice Leonard Lake tortured, killed and buried 11 people in northern California between 1984 and 1985. After the men were arrested for shoplifting, police found bullets and a silencer in their car and took them into the police station for questioning. Lake killed himself there with a cyanide pill. Ng was later sentenced to death. Hide Caption 16 of 26 Photos: Infamous serial killers Robert Lee Yates Jr. killed 15 people, most of them between 1996 and 1998. He buried one of them in a flower bed by his house in the Spokane, Washington, area. Most of his victims were prostitutes or drug addicts he killed in his van. He is on Washington's death row. Hide Caption 17 of 26 Photos: Infamous serial killers Gary Leon Ridgway, also known as the Green River Killer, confessed to 48 killings after his DNA was linked to a few of his victims. Remains of his victims, mostly runaways and prostitutes, turned up in ravines, rivers, airports and freeways in the Pacific Northwest. Hide Caption 18 of 26 Photos: Infamous serial killers Aileen Wuornos was executed in Florida in 2002 for the murders of seven men whom she had lured by posing as a prostitute or a distressed traveler. Hide Caption 19 of 26 Photos: Infamous serial killers Derrick Todd Lee was accused of raping and killing six women in Baton Rouge, Louisiana, between 2001 and 2003. He was arrested in Atlanta for the murder of Charlotte Murray Pace, convicted in 2004 and sentenced to death. Hide Caption 20 of 26 Photos: Infamous serial killers Danny Rolling pleaded guilty to the 1990 murders of five students he raped, tortured and mutilated in Gainesville, Florida. Rolling was also found responsible for a 1991 triple homicide in Shreveport, Louisiana, and was executed in 2006. Hide Caption 21 of 26 Photos: Infamous serial killers Angel Maturino Resendez, also known as the Railway Killer, was a drifter from Mexico. During the 1990s, he would rob and kill his victims near railroad tracks on both sides of the border and then hop rail cars to escape. Resendez was executed in 2006. Hide Caption 22 of 26 Photos: Infamous serial killers Pig farmer Robert Pickton was charged with 26 counts of murder after police found the bodies of young women on his farm in Port Coquitlam, British Columbia. He was convicted of six murders in 2007, and he is serving a life sentence. Hide Caption 23 of 26 Photos: Infamous serial killers The BTK Strangler, Dennis Rader, killed 10 people between 1977 and 1991 in the Wichita, Kansas, area. He was sentenced to 10 consecutive life terms in 2005. Rader named himself BTK, short for "bind, torture, kill." Hide Caption 24 of 26 Photos: Infamous serial killers Police found the decomposing and buried bodies of 10 women and the skull of another woman at the Cleveland home of ex-Marine Anthony Sowell. He was convicted and given the death penalty in 2011. Hide Caption 25 of 26 Photos: Infamous serial killers Chester Dewayne Turner was sentenced to death for murdering 14 women and one victim's unborn fetus in the Los Angeles area between 1987 and 1998. Turner was later convicted and sentenced to death for four more murders. Hide Caption 26 of 26

"I somewhat follow the news, but there has been no time in the last 40+ years when someone was not (stirring) the pot," Hartnell wrote to CNN in an email.

Hartnell was stabbed eight times, and Shephard, between 10 and 20 times. She died a day later at the hospital, but was able to give a description of the attacker before she died.

Stewart was born in New Orleans and abandoned as a newborn in a stairwell of Baton Rouge apartment building. He was later adopted and "had an idyllic childhood," the publisher said.

About 10 years ago, when he was 39, Stewart's birth mother, Judy, contacted him for the first time. He then began his search for his biological father, with whom his mother hadn't been in contact since Stewart was abandoned.

Stewart, who is married with a child, kept a journal during the search, which became the basis for the book. Stewart has bachelor's degree in electrical engineering from Louisiana State University.

His book, "The Most Dangerous Animal of All: Searching for My Father ... and Finding the Zodiac Killer," was co-written with journalist Susan Mustafa.

"Stewart and Mustafa construct a chilling psychological profile of Stewart's father: as a boy with disturbing fixations, as a frustrated intellectual with pretensions to high culture, and as an inappropriate suitor and then jilted lover unable to process his rage," the publisher said.

HarperCollins publicist Tina Andreadis told New York Magazine that "Stewart's father had a criminal record in San Francisco ('forgeries, bad checks'), and there was a strong resemblance between his father's mug shot and the police sketch," the magazine said.

"If you look at Gary's photo next to the sketch of the Zodiac (killer) next to his father's mug shot, you can see that there is very clearly more than just a passing resemblance," Andreadis told the magazine. "They look alike."

The Zodiac Killer craved attention and wrote several letters to newspapers taking credit for his crimes. He also included cryptograms or ciphers that he claimed would shed light on his identity.

But he was never caught.

The unsolved case inspired the 2007 film "Zodiac," starring Jake Gyllenhaal, Robert Downey Jr. and Mark Ruffalo.