SAN FRANCISCO (KGO) -- The Pittsburgh shooting is part of a series of recent attacks against American Jews.
"We saw today in Pittsburg what we believe to be the deadliest attack, the deadliest anti-Semitic attack, that's occurred in the United States," said Seth Brysk, the northern California regional director of the Anti-Defamation League, or ADL.
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The ADL said they've seen a spike in hate crimes against American Jews going back to the 2016 presidential campaign. Their latest report shows a nearly 60 percent increase in anti-Semitic incidents from 2016 to 2017, the largest single-year increase on record.
That covers "not only criminal activity, it's also legal expressions of hatred. So it could be somebody saying or doing something using their free speech rights," Brysk explained.
Even here in the Bay Area, there has been an upward trend in anti-Semitism. In September during the Jewish new year, fliers with anti-Semitic messages and images were posted at five East Bay synagogues.
RELATED: Anti-Semitic flyers found at five East Bay synagogues ahead of Jewish High Holidays
Brysk said white supremacists are trying to mainstream their cause by sanitizing their message.
"(They are) using the terminology of the civil rights movement, so they talk about white rights, they talk about pride in being white, they try to attach it to legitimate issues of debate, like immigration," Brysk said. He said Jews have been demonized and blamed for a variety of society's problems. And that leads to fear.
"There is a correlation between hate crimes and the statement and positions of public leaders," said UC Hastings law professor George Bisharat.
He said when President Trumps demonizes Mexicans or Muslims or athletes, it emboldens people to act.
"This suggests to people that hateful sentiments are not only permissible, they are approved by the highest leader in our country," Bisharat said.
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The Pittsburgh synagogue shooter, Robert Bowers, complained on social media about HIAS, a Jewish group that advocates for refugees. Before the shooting, Bowers posted on social media: "HIAS likes to bring invaders in that kill our people. I can't sit by and watch my people get slaughtered. Screw your optics, I'm going in."
"This is exactly the kind of fear that drives people to violence. It's not, in other words, just a matter of hate. Fear is a very important factor," Bisharat explained.
Regardless of motive, Brysk said this shouldn't be seen as an isolated incident: "It may not target your community today, but it does affect us all."
Major spike in anti-Semitic incidents since 2016 election, Anti-Defamation League says