(CNN) Tipsters alerted the FBI to a threatening post on the anonymous message board 8chan minutes before a gunman opened fire at a California synagogue, an FBI official told CNN Monday.

The post was written by someone using the same name as the 19-year-old who would later be arrested in the shooting at the Congregation Chabad in Poway, north of San Diego.

The FBI official said several tips came in to its tip website and phone line approximately five minutes before John T. Earnest allegedly began shooting. He opened fire at 11:23 a.m. local time, according to the San Diego Sheriff's office.

Earnest was charged on Monday with one count of first-degree murder, three counts of first-degree attempted murder and arson of a house of worship, according to authorities. All murder and attempted murder charges come with a hate crime special circumstance and gun allegations.

He is scheduled to be arraigned on Tuesday in San Diego County Superior Court.

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