The man authorities believe killed 11 people inside a Pittsburgh synagogue had a history of posting racist, anti-immigrant, and anti-Semitic rants — and broadcast his violent intentions Saturday shortly before entering the house of worship with guns blazing.

In a post on the Twitter-like social media platform called Gab, Robert Bowers ranted about the Hebrew Immigrant Aid Society, a non-profit that helps resettle immigrants and refugees.

“HIAS likes to bring invaders in that kill our people,” Bowers, 46, wrote about an hour before officials say he took aim at congregants inside the Tree of Life Synagogue. “I can’t sit by and watch my people get slaughtered.”

Bowers didn’t mention the synagogue, but chillingly added: “Screw your optics, I’m going in.”

Officials said Bowers used an “assault rifle” and had three handguns on him when he surrendered to police after the bloodbath in the synagogue. He was wounded by police, but the nature of his injuries was not immediately revealed.

A licensed gun owner who legally purchased at least six guns since 1996, Bowers had no criminal record and was “unknown to law enforcement” before the massacre, according to Special Agent Bob Jones of the FBI’s Pittsburgh office. “The suspect’s full motive is unknown but we believe he was acting alone,” Jones added.

Beyond his virulent anti-Semitism— and apparent love for guns — little was immediately known about Bowers, who lives in an unremarkable apartment in the Baldwin section of Pittsburgh’s South Hills, a middle-class area of the city. Neighbors at one of his last known addresses told the Pittsburgh Post Gazette he frequented the home and may have cared for a disabled person there.

Online sleuths identified him as a rabid user on Gab, called an alt-right alternative to similar sites.

Bowers’ since-deleted profile page under the name @onedingo branded Jews “the children of Satan.”

He created his Gab profile in January, but had already posted 627 messages on the site, disturbing comments such as: “Daily reminder: Diversity means chasing down the last white person.”

He frequently re-posted anti-Jewish memes, including several that questioned the Holocaust.

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