In his two years in office, Trump has done plenty to legitimize views previously considered too extreme for political discourse—and that, in turn, has opened the door for political violence.

Vigil participants hold candles and sing a Jewish prayer in front of the White House on October 27th, 2018, during a vigil for the victims of the Tree of Life Congregation shooting. (Photo: Alex Edelman/Getty Images)

On Saturday, a man who authorities have identified as Robert Bowers shot and killed at least 11 worshippers assembled at the Tree of Life Congregation in Pittsburgh, Pennsylvania. Witnesses say Bowers, 46, was shouting anti-Semitic slurs as he opened fire in the synagogue; four police officers were wounded before he was arrested.

Bowers has a history of anti-Semitism: He was a frequent poster on Gab, the social media network that's become a haven for white nationalists. There he derided Jews for bringing "evil" Muslims and "invaders" into the United States.

The shooting, which ranks as the deadliest against Jews in American history, didn't somehow appear out of the ether. In February, the Anti-Defamation League reported that anti-Semitic incidents had skyrocketed by 57 percent over the previous year, with more than 2,000 cases of harassment or assault recorded in 2017. That made the latest report the highest incident level in more than two decades. That Gab was part of Bowers' story is unsurprising given the rise of digital enclaves: These spaces (and the companies that empower them) have, for years, proven to be havens for hate groups to organize, harass, and intimidate. An ADL report on the state of online discourse, released the day before the Pittsburgh massacre, put it more bluntly: "[T]he online public sphere—now a primary arena for communication about American politics—has become progressively unhospitable [sic] for Jewish Americans."

It would be negligent to discuss the shooting—and the general rise in anti-Semitism in this country—without talking about President Donald Trump. It's not hard to consider that, in his two years in office, Trump has done plenty to legitimize views previously considered too extreme for political discourse—and that, in turn, has opened the door for political violence.

Indeed, the complacency shown toward white nationalism in Trump's declaration that the Charlottesville protesters who chanted "Jews will not replace us" were, in fact, "very fine people" was on display during this chaotic week: He not only cast doubt on the 14 pipe bombs sent by one of his devotees to news organizations and Democratic figureheads, but initially suggested that, had the Tree of Life congregants been armed, perhaps Saturday's tragedy could have been avoided. When Trump decries political violence, but invokes George Soros and spurs on chants of "CNN sucks," he's only further facilitating a culture of animosity—and, in extreme cases, violence—in a country that was already plagued by violence and animosity to begin with.

Trump's nod-and-wink practice is known in political science circles as "stochastic terrorism," the use of mass communication to "incite random actors to carry out violent or terrorist acts that are statistically predictable but individually unpredictable." And this has been the Trump playbook for years. In August of 2016, Trump dropped an alarming suggestion to a crowd in Wilmington, North Carolina, regarding the prospect of Hillary Clinton picking judges and Supreme Court justices. "If she gets to pick her judges, nothing you can do, folks," he said. "Although the Second Amendment people, maybe there is. I don't know." When it comes to shootings, there are no lone wolves; every shooter is, to some degree, a product of his time. Trump, as David Cohen put it in Rolling Stone, "puts out the dog whistle knowing that some dog will hear it, even though he doesn't know which dog."

Just days before the Tree of Life shooting, at least 14 pipe bombs were sent through the mail to various media outlets and Democratic critics of Trump. Police arrested the suspect, Cesar Altieri Sayoc, on Friday; acquaintances say Sayoc had embraced white nationalist views and apparently saw Trump as a sort of father figure. Then there's Gregory Bush, the 51-year-old gunman who killed two African Americans last week in a supermarket in Kentucky (authorities are investigating the attack as a possible hate crime); Bush reportedly spared a white bystander in the market, telling him that "whites don't kill whites."

These are, of course, separate instances with unique sets of circumstances. But they do all share one thread: hostility toward some sort of "other." That's a theme Trump has long wielded for his own political gains—even if it carries a bloody cost.