The teenage San Diego mosque gunmen appear to have left behind a 𝓈𝒽𝓸𝒸𝓀𝒾𝓃𝑔, hate-filled manifesto, which praised Adolf Hitler and a slew of mass murderers, before the attack, The California Post has learned.

Authorities are investigating whether 17-year-old Cain Clark and 19-year-old Caleb Vasquez wrote the nihilistic missive before killing three people and then each other, according to law enforcement sources.

The document espouses a desire to spark a race war and bring about the end of civilization.

The shooters idolized the New Zealand shooter Brenton Tarrant and named their manifesto after him.Obtained by CA Post

Cain Clark.Instagram/madison.warhawk.wrestling

The 75-page document is laden with the same Nazi iconography that Clark was seen wearing during a horrifying livestream video of the attack, including the Black Sun, which is associated with Nazi SS head Heinrich Himmler, and Atomwaffen, which is tied to a violent neo-Nazi group.

The opinions therein are a nonsensical collection of anti-Trump, anti-liberal, antisemitic, homophobic and mysoginst bile — tied together only by the authors’ fury that they were not given more in life.

Sources said investigators have a copy of the purported manifesto and believe it to be authentic.

Jennifer Du, who lives across the street from Clark’s $750,000 SoCal home, recalled seeing the 17-year-old a day before they opened fire inside the Islamic Center.

A fuel can with the Nazi SS symbol on found near the shooter’s dead bodies.Anadolu via Getty Images

“It’s been unreal. I saw him literally the day before. He just stood there,” Du, 30, told The California Post.

“I didn’t know if he was watching me or something, but he just got food delivery and went back in.”

Clark’s next door neighbor in San Diego described his family as normal, noting that the teen practiced martial arts and recalled seeing him in a karate outfit.

A still from the livestream moments before Cain shoots Vasquez dead and turns the gun on himself.Obtained by CA Post

“As far as we knew he was very nice. They were a nice family,” said the neighbor, Marne, 85, who declined to provide her last name.

“We were just flabbergasted,” she added of finding out about the attack. “We thought, ‘Oh my god,’ we couldn’t believe it. Just flabbergasted.”

A section, believed to have been written by Clark, describes his views as neither left- nor right-wing, and voiced seething disdain for both sides.

The cover of Vasquez’s section of the manifesto.Obtained by CA Post

He claimed to align ideologically with Hitler, and said he drew inspiration from for the horrific 𝒶𝓈𝓈𝒶𝓊𝓁𝓉 on the mosque from ideologically driven mass murderers including Ted Kaczynski, Timothy McVeigh and Norwegian terrorist Anders Breivik.

Clark describes the 2019 New Zealand Christchurch mosque shooter as the blueprint for livestreaming the terror attack, which they hoped would be widely shared and serve to motivate others to carry out similar deadly strikes. He referred to the gunman as “Saint Terrant.”

One of the shooter’s weapons, a shotgun, seen with hateful messages scrawled on it.Anadolu via Getty Images

The unhinged dispatch contains a scattershot of derogatory and racist views targeting a number of groups — including Muslims, Jews, and gay people, among others, describing himself as an “accelerationist” who hoped to instigate an “all-out race war” to bring about the collapse of society.

In Vasquez’s portion he lamented being short, which he said caused him great pain and humiliation.

Clark also chillingly stated that he felt no remorse for his actions and wrote that, had he survived, he would have allowed his lawyers to handle everything afterward.

The San Diego house where Cain Clark lived with his mother.Rafael Fontoura for CA Post

He also denied carrying out the attack for fame, admitting he personally hated the victims and other cultures, and said he did not intend to survive the shooting.

Online profiles linked to Clark featured multiple Nazi slogans, and images of Hitler and German soldiers in formation during World War II.

Clark and Vazquez gunned down three people on Monday, including security guard and father of eight Amin Abdullah, who police say prevented more deaths. An online fundraiser for the slain hero raised nearly $2 million in less than 24 hours.

Left: The Black Sun symbol, originating in Nazi Germany. Right: The Atomwaffen Division logo, a shield with a radiation symbol, similar to a Waffen SS divisional insignia.Wikipedia/ADL

Two other members of the mosque, Nader Awad and Mansoor Kazziha, were identified as victims of the shooting.

At least one of the suspects took a weapon from his parents’ home and left a suicide note that talked about racial pride, a law enforcement source said.

After the shooting, the livestream appeared to show Clark shoot Vazquez twice in the head before taking his own life.

Police and the FBI are actively investigating the massacre and will be executing search warrants in the coming days, a source familiar with the case told The Post.