[narrator]
near Blue Rock Springs.
[Rust]
the call came over the radio,
possible shots fired out in the Blue Rock Springs area.
[narrator]
that lies just minutes from Lake Herman Road.
As he arrives, he sees a body on the ground.
We immediately saw this guy's all bloody,
and he'd been shot somewhere in the face or neck area,
and just blood all over him. He's moaning and...
[narrator]
Rust finds a young woman slumped over the steering wheel
and shot multiple times in the back.
The attack is less than an hour old
when police take a call from a man
claiming to be the Rock Springs shooter.
He said something to the effect that there's been, uh...
two persons shot out at the park
and he said something to the effect
that, "I also shot those two kids last year."
And then he said,
kind of tauntingly, "Goodbye!"
[narrator]
just blocks from the police department.
The receiver hangs off the hook,
but no usable prints are lifted.
-[disconnect tone] -[ominous musical sting]
In the editorial room of the
a curious state of affairs is developing.
The board of editors is on the receiving end of a letter
from a man claiming to be the Vallejo killer,
and offering intimate details of the crimes as proof.
The missive is double posted,
marked "Please rush to editor"
and signed with a crossed circle.
A mark that would later become known as the Zodiac symbol.
In 1969,
Robert Graysmith is editorial cartoonist for the paper.
We started getting these very bizarre letters
and they're codes and threats,
and the guy's saying, "You print this code in your paper..."
And he sent one to each of the major papers.
"...or I'm going on a killing rampage."
That's just simply-- We'd never seen anything like this.
[narrator]
are eight lines long,
each containing seventeen symbols.
The killer claims that if decoded,
these ciphers will reveal his identity.
[Graysmith]
The NSA, the FBI, nobody could break them.
But a high school teacher in Salinas, California,
sat down with his wife over the weekend,
and they simply did not let up, and they found the motive
for the killer's crimes.
[narrator]
Donald and Bettye Harden unlock the key to the code.
It reveals not the killer's name,
but his motive for killing.
What Harden came up with, off the top of my head,
it's, "I like killing because killing people
is the most dangerous game in the world."
[narrator]
in the most dangerous game of serial murder,
played by a man who would soon be known to the world
as the Zodiac.
[ominous music playing]
On September 27th, 1969,
Cecelia Shepard and Bryan Hartnell
are attacked as they picnic on the shores of Lake Berryessa.
Their assailant wields a knife
and wears an executioner's hood
with the Zodiac symbol on his chest.
Cecelia dies from multiple stab wounds.
Bryan lives but never sees the Zodiac's face.
On that same day,
36-year-old Arthur Leigh Allen
tells family members he's going scuba diving in Lake Berryessa.
He returns that evening covered in blood
with a knife in the front seat of his car.
A tip is phoned in to police:
"Take a look at Arthur Leigh Allen as the Zodiac."
A friend named Don Cheney claims
Allen called himself the Zodiac
before the term had ever been made public by the killer.
[man]
with a gun with a flashlight tied to it
so he could shoot 'em.
And he told Cheney, he says,
"I think I'll call myself the Zodiac."
[narrator]
investigators question Allen about the killings.
First words out of his mouth, "The Most Dangerous Game."
They say, "My God, what's that?"
"It's my favorite book. I've loved it since the 10th grade."
This was about a guy named Count Zaroff,
very similar name to Zodiac,
who dressed like Zodiac, all in black,
who hunted couples through the woods,
carried a gun, carried a knife, carried a bow and arrow.
[narrator]
Arthur Leigh Allen is right out of Central Casting.
A white male, early 30s,
a loner with an IQ near genius level,
and a love for guns.
With no print match however,
and no other forensic evidence,
the investigation loses steam.
The Zodiac killings stop
and the cases go cold.
In the summer of 1992,
George Bawart is hard at work trying to make a case
for Arthur Allen as the Zodiac Killer
when he gets a call.
[Bawart]
from a cop named Terry Baron.
"Hey, George, you still looking at Arthur Leigh Allen
as the Zodiac?" I said, "Yeah."
He said, "I'm in his living room."
I said, "What are you doing there?"
"He's on the floor dead."
[narrator]
Before his body is committed to the ground,
Bawart orders an autopsy.
[Bawart]
so we could have tissue, so we could get DNA.
[narrator]
but he wants to be prepared.
Samples of Allen's brain are frozen
and stored for future testing,
in case some day cold case detectives
ever run down a sample of the Zodiac's DNA.
[ominous music playing]
Carroll Kelly is a homicide detective
with the San Francisco Police Department.
Like everyone else in the department,
Carroll is familiar with the legend of the Zodiac.
Carroll pulls the case files
and quickly realizes his best hope for success
lies with forensics.
The idea that a criminal would be aware
of fingerprints and things like that,
and take efforts to hide or conceal or mask them
is reasonable.
Um, but the idea that they would be aware of DNA
and try to hide that is not reasonable.
[narrator]
took no precautions against DNA transfer.
Before a letter can be analyzed, however,
a threshold determination must be made.
Which of the 20 so-called Zodiac letters
can be considered authentic and thus worth testing?
Susan Morton is a forensic document examiner
with the San Francisco Police Department.
When you write, you rest the heel of your palm,
a very characteristic part of it, on the paper.
And people in those days weren't really aware
that you could leave a palm print
and that it could be identified.
They knew about fingerprints,
but the public really wasn't that aware of palm prints.
[narrator]
One is discovered in his final authenticated letter.
They were able to obtain palm prints from Arthur Leigh Allen.
It was compared to the one that had been developed earlier
and they don't match.
That is not Arthur Allen's palm print.
[narrator]
and no handwriting link to Arthur Leigh Allen.
The tools of modern forensic science
appear to clear Allen
as a major suspect in the Zodiac case,
frustrating cold case detectives
and adding yet another layer of intrigue
to a case and a killer, that for millions,
has now become an obsession.
In truth, every detective I think would like to have
their Dr. Moriarty.
And in the case of Zodiac,
you have the worthy adversary.
[narrator]
for the Zodiac.
He is either dead or in prison.
Either way, the job of IDing the killer
and, if possible,
holding him accountable for his crimes,
is an important one for the simplest of reasons.
Five families
for whom the Zodiac is neither legend nor movie star,
nor cult figure.
But a real-life killer.
A man who took the life of a brother or sister,
daughter, son, or friend.
[Carroll]
and again, talking with the families,
you are reminded constantly
of the lifelong devastating effect
that-that these crimes have on people.
The people that survive.