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PHILADELPHIA (CBS) — The alleged gunman in the deadly Pittsburgh synagogue shooting reportedly posted anti-Semitic rants on a popular website with the alt-right, called “Gab.” It has since been shut down, but not without opposition.

The social media website has been taken offline after revelations that Robert Bowers allegedly used the site to threaten Jews. Right before walking into the Tree of Life Synagogue, Bowers allegedly logged onto Gab and wrote, “I can’t sit by and watch my people get slaughtered. Screw your optics, I’m going in.”

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“If someone would’ve seen the string of posts, and the true hatred that he had, and certainly it was very clear that last post that he made, although it was only a few minutes before he went into the synagogue, it was clear, he said I’m gonna do something about it and he did,” said Nancy Baron-Baer, regional director of the Anti-Defamation League.

She continued, “Bowers was not alone in using the site. It has been used by many that have been exclaiming their anti-Semitism, their racism, their homophobia online.”

Andrew Torba, Gab’s founder and CEO, fired back at critics by posting a statement online, reading in part, “Gab isn’t going anywhere. We have plenty of options, resources and support. We will exercise every possible avenue to keep Gab online and defend free speech.”

“ADL has always been a big believer of freedom of speech, freedom of press, freedom of religion, etc., but you know there is a point at which it’s no longer free speech, it becomes vile and insightful and dangerous,” said Baron-Baer.

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Bowers allegedly used anti-Semitic slurs on Gab and posted pictures of his handgun collection. Gab said on Twitter that it had been banned by payment processing firms PayPal and Stripe, which were used for donations to keep the site running. It was also banned from hosting service Joyent and domain register GoDaddy.

While heading into a Philadelphia synagogue for a prayer vigil on Sunday, Pennsylvania Attorney General Josh Shapiro says he, too, plans to take action.

“We’re also going to be conducting, independently, a review of the social media platform Gab,” said Shapiro.