The deadly shootings targeting synagogues in California and Pittsburgh have raised concerns that anti-Semitic hatred is increasingly a rallying point for America's resurgent white supremacists.
On Saturday a teenage gunman who wrote a hate-filled manifesto online opened fire at a synagogue in Poway, California, leaving one woman dead and three others injured, including a rabbi.
The latest assault came exactly six months after another man spouting anti-Semitic vitriol shot dead 11 and injured six others at a synagogue in Pittsburgh.
And it ignited questions over whether American white supremacists, long overlooked by US law enforcement, are turning their focus on the Jewish community over other targets.
In both incidents, the attackers were part of a broader, internet-based far-right community that espouses hate against Muslims, blacks, immigrants and Jews, and advocate for a Caucasian, Christian society based on European culture.
Analysts say certain websites, particularly the 8chan and Gab messaging platforms, have become breeding grounds for white extremists, encouraging hate and violence against a range of targets including Jews, tapping into age-old anti-Semitic stereotypes.
"The alleged attacker's disturbing letter is more than just a hateful tirade," Rita Katz, who researches violent extremism, said of the Poway attack.
"It is a product of white nationalist ideology, using specific jargon, points of argument, online meme references, etc. Further proof of how dangerous far-right rhetoric is in inspiring attacks," she wrote on Twitter.
- Rising number of incidents -
Research by the Southern Poverty Law Center and other groups shows that in recent years the number of US incidents involving far right extremists and white nationalists have easily surpassed those of Muslim extremists.
"Once again, a young white male has apparently been influenced by dangerous online white supremacist propaganda. And once again, we see how this propaganda can lead to terrorist acts," said Heidi Beirich, Intelligence Project Director at the SPLC.
White supremacists have gotten tacit encouragement from President Donald Trump, who has been accused of failing to unequivocally condemn their ideology, and whose own anti-immigration policies have targeted most heavily Muslims, Africans and Latinos.
Daryl Johnson, a former senior domestic terrorism analyst at the Department of Homeland Security, explains that the white supremacist movement involves many individuals and factions.
For someone subscribing to the broader ideology, their choice of a target can arise from their particular experience or neighborhood, he said.
Yet anti-Semitism -- which Trump has repeatedly spoken out against -- has become a particular hallmark of this community.
One common thread stands out among white extremists on the internet, according to Johnson: the prevalence of global conspiracy theories about Jews.
Cesar Sayoc, a Trump supporter who mailed 16 crude bombs last year to prominent Democrats, reportedly ranted to colleagues about Jews as well as blacks and gays.
Jeffrey Clark, a white nationalist arrested in Washington on gun charges last year, was a follower of the Pittsburgh synagogue shooter and, according to court documents, together with his brother "fantasized about killing Jews and blacks."
A Coast Guard officer, Christopher Hasson, arrested in Maryland near the US capital in February on drug charges, was discovered to have a personal arsenal of combat weapons and neo-Nazi sympathies, and had written about undertaking a mass attack.
Two days after the Poway attack, there was a huge number of crude and violent anti-Semitic postings on 8chan, the site where the Poway shooter himself is believed to have posted a statement ahead of the attacks.
And yet, analysts say, the spike in anti-Semitic attacks and hate speech in the United States should be viewed in the context of surging right-wing extremism -- whose targets are by no means limited to Jews.
The Poway attacker, for instance, may also have attempted to set a nearby mosque on fire in March according to police.