An anti-Semitic open letter posted under the name of a man suspected of opening fire at a synagogue near San Diego Saturday was left on a far-right message board hours before the attack.

San Diego police said one person was killed and three were injured in the Saturday morning shooting at the Chabad of Poway on the last day of Passover.

A suspect, John T. Earnest, 19, of San Diego, was taken into custody after the shooting, authorities said.

A user identifying himself as John Earnest posted a white nationalist open letter to the far-right message board 8chan. He also used the username "JohnTEarnest" to post the letter on a document hosting site.

The link to the anti-Semitic note was put online shortly after 9 a.m. Saturday and posted to 8chan, along with a link to a Facebook page and says "a livestream will begin shortly."

There is no active link to a livestream on his Facebook page. The post also includes a link of songs the poster planned to play during the stream.

The 8chan post appears near identical to the one Brenton Tarrant left hours before opening fire at a mosque in Christchurch, New Zealand. It even links to the same document dumping sites PasteBin and MediaFire to host the open letter.

The attached note is similar in both format and tone to the one written by Tarrant, who killed 50 people last month. Tarrant and Pittsburgh synagogue shooter Robert Bowers are listed as a direct inspiration in the letter, which is riddled with almost exclusively anti-Semitic tropes and advocacy for white supremacy.

The letter claims the shooter began planning his attack shortly after Tarrant's attack. Like Tarrant's post, it follows a question-and-answer format.

The shooter claims in the Q-and-A section to eschew political ideology, saying he does not support Donald Trump because of his support for Israel. The writer also complains that conservatives aren't violent enough in support of their politics.

Shortly after the post, 8chan users cheered on the poster of the note. The first response encouraged the user to "get a high score." The letter repeatedly credits 8chan with the writer's radicalization.

Facebook removed the profile linked by 8chan several hours after the shooting. Before the page was pulled down, white nationalists descended on the page, leaving messages for the shooter.

The shooting outside San Diego occurred six months to the day after Robert Bowers, an anti-Semitic white nationalist who frequented extremist forums, killed 11 people at a synagogue in Pittsburgh.