Before opening fire on a synagogue full of people in Pittsburgh on Saturday, killing 11 and injuring six others, including four police officers, suspected gunman Robert Bowers reportedly yelled, “All Jews must die!”

The 48-year-old Bowers, who was taken into police custody after the shooting at the Tree of Life Congregation synagogue, is believed to have acted alone in what the Anti-Defamation League (ADL) said is “likely the deadliest attack on the Jewish community in the history of the United States.”

“It is simply unconscionable for Jews to be targeted during worship on a Sabbath morning, and unthinkable that it would happen in the United States of America in this day and age,” ADL CEO Jonathan Greenblatt said in a statement Saturday. “Unfortunately, this violent attack — the deadliest anti-Semitic attack in the United States since 2014 — occurs at time when ADL has reported a historic increase in both anti-Semitic incidents and anti-Semitic online harassment.”

A man is escorted out of the Tree of Life Congregation synagogue by police following a shooting at the Pittsburgh synagogue, Oct. 27, 2018. (Photo: Alexandra Wimley/Pittsburgh Post-Gazette via AP)

The earlier incident referenced by Greenblatt was the 2014 shooting , by a former Ku Klux Klan “grand dragon” and neo-Nazi, at two Jewish community centers outside Kansas City that left three people dead.

Since then, organizations like the ADL and others observed a dramatic rise in anti-Semitism in the United States. In its annual Audit of Anti-Semitic Incidents , the ADL reported nearly 2,000 cases of harassment, vandalism and physical assault targeting Jews in 2017 — 57 percent more than the year before. It was the largest single-year increase since the organization first began tracking such data in 1979, and it marked the highest number of anti-Semitic incidents on record since 1994. In particular, anti-Semitic incidents in schools and college campuses nearly doubled in 2017 for the second year in a row, contributing in part to the overall spike last year. Some of the incidents in the ADL report came from the left, in the form of “references, accusations and conspiracy theories” directed against Jews over “purported support for Israel.”

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Toppled and damaged headstones rest on the ground at Mount Carmel Cemetery in Philadelphia, Feb. 27, 2017. The Anti-Defamation League found an increase in cases of anti-Semitic intimidation and vandalism in 2016, evidence that anti-Jewish bias intensified during the election. (Photo: Jacqueline Larma/AP)

“Without a doubt, we’ve seen an increase in anti-Semitic incidents,” said Adam Hertzman, director of marketing for the Jewish Federation of Greater Pittsburgh. Hertzman told Yahoo News on Saturday that “in general, Pittsburgh has been one of the safest cities, in terms of the Jewish community, in the United States,” but the city has not been exempt from this national trend. Two years ago, he said, the Jewish Federation hired a Jewish Community security director in response to the rise in such incidents, which has included the dissemination of neo-Nazi literature and imagery, such as swastikas.

“Largely it has not been incidents of violence,” he said, adding that that is “one of the reasons we’re more shocked at this situation,” referring to Saturday’s shooting.

In another recent study published on Friday, the researchers with the ADL found a significant increase in online attacks targeting Jewish politicians, journalists and others in the lead-up to next month’s midterm elections. The report found that both robot and human-run accounts were responsible for anti-Semitic tweets, leading researchers to conclude, “Both anonymity and automation have been used in online propaganda offensives against the Jewish community during the 2018 midterms.”

Bowers appears to have participated in his trend. Among other social media networks, the suspect in Saturday’s shooting was active on Gab, a site popular among white supremacists, neo-Nazis and other far-right extremists.

Robert Bowers’s Pennsylvania driver’s license photo. (Photo: PA Dept. of Transportation)

Bowers’s account was quickly deactivated shortly after his name was made public, but a link to his archived profile offers a glimpse at the kind of anti-Semitic rhetoric he posted, beginning with the line “jews are the children of satan” in his user bio. Two of his most recent posts, including one apparently posted this morning, refer to HIAS, the Hebrew Immigrant Aid Society, a nonprofit that provides humanitarian aid to refugees in the U.S.

According to a statement published on Medium , Gab administrators said they had suspended Bowers’s profile once they were alerted to a verified account matching the name of the suspected shooter, first backing up the user data on Bowers’s account and then alerting the FBI to its existence.

“We are ready and willing to work with law enforcement to see to it that justice is served,” they wrote, adding, “Gab unequivocally disavows and condemns all acts of terrorism and violence.”

The statement attempts to dispel negative perceptions of the Gab community, insisting that the social network’s “mission is very simple: to defend free expression and individual liberty online for all people.” But Bowers’s views are common on Gab. Many of the anti-Semitic posts found in Bowers’s archived feed had been reposted from the accounts of other Gab users.

White supremacists march with tiki torches through the University of Virginia campus in Charlottesville, Aug. 11, 2017. (Photo: Zach D. Roberts/NurPhoto via Getty Images)

The ADL study on anti-Semitism leading up to the 2018 midterms also suggested a link between the rise in such attacks and the election of President Trump. Prior to the 2016 election, “anti-Semitic harassment and attacks were rare and unexpected, even for Jewish Americans who were prominently situated in the public eye,” states the report. “Following his election, anti-Semitism has become normalized and harassment is a daily occurrence.”

One of the most frequently attacked individuals is George Soros, the billionaire philanthropist who was among the targets of pipe bombs sent to prominent Democrats and members of the media earlier this week. A Florida man who identifies as a Trump supporter was arrested Friday in connection with the attempted bombings.

Bowers, judging from his postings, was not a fan of Trump, whom he evidently considered insufficiently tough on foreigners, writing, “Trump is a globalist, not a nationalist. There is no #MAGA as long as there is a kike infestation.”

Trump’s daughter Ivanka and her husband, Jared Kushner, are observant Jews.

First responders stand outside the Tree of Life synagogue in Pittsburgh, where a shooter opened fire on Oct. 27, 2018. (Photo: Gene J. Puskar/AP)

Following initial reports of Saturday’s shooting, Heidi Beirich, director of the Southern Poverty Law Center’s Intelligence Project, speculated to Yahoo News about what the gunman — whose identity was unknown at that point — might have in common with Cesar Altieri Sayoc , the suspect arrested Friday in the attempted mail bombings.

“Once again, we’ve seen people … who are motivated by extremist ideas and ideologies willing to be engaged in violence,” said Beirich.

“We have way too much domestic terrorism emerging from white supremacists and far-right extremists,” she continued, adding that while “that’s been going on for a long time, it doesn’t help when Trump stokes these things.”

Trump has faced criticism for his response to the mailings of the pipe bombs, which were sent to high-profile critics of the president and frequent subjects of his own attacks.

After initially suggesting that Saturday’s deadly events could have been avoided “if they had some kind of a protection inside the temple,” Trump later struck a more sympathetic tone at the annual Future Farmers of America convention in Indianapolis, where he condemned the shootings as “pure evil” and referred to them as “an anti-Semitic act.”

“You wouldn’t think this would be possible in this day and age, but we just don’t seem to learn from the past,” he said, before launching into another denunciation of globalists.

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