FBI hate-crime statistics for 2016, the most recent year available, show that more than half of reported antireligious hate crimes in the United States were motivated by anti-Semitism. That’s been consistent in recent years, while bias against Muslims, who make up about 1 percent of Americans, was responsible for about a fifth of hate crimes.

And anti-Jewish crime may be rising. The Anti-Defamation League, a century-old advocacy group for Jews and other people targeted by discrimination, found that 2017 saw a nearly 60 percent surge in reported anti-Semitic incidents—which came on top of a 35 percent increase the year before. In part, the group notes, the rise could be driven by more people reporting to the ADL. But the higher numbers reversed a long-term downward trend. And a wave of bomb threats that terrorized schools and community centers was blamed, at least in part, on an Israeli American teen convicted in June.

Chants of “Jews will not replace us” punctuated the infamous “Unite the Right” rally in Charlottesville last year, which also saw seven Jewish cemeteries desecrated. The physical assaults the ADL recorded included those of an elderly man at a Jewish retirement home, a 12-year-old boy on his way home from Friday prayers, a woman in a taxi, a person on a subway train, and a man who was attacked and maced while waiting at a red light.

Read: Why Charlottesville marchers were obsessed with Jews.

Public anti-Semitism has shown a sustained increase among alt-right white nationalists since President Trump’s 2016 election and has continued through this midterm election campaign, according to an ADL report published this month. Jewish Americans with a public presence, ranging from public officials to journalists to professors, say that such harassment has moved from rare to commonplace over the past three years. Twitter was uniformly cited as the worst platform, with one interviewee calling it “ideally designed for organized or non-organized harassment.”

The suspect in Saturday’s attack reportedly used the social network Gab, which has a reputation as a platform for people banned by Twitter. Minutes before entering the synagogue, the suspect allegedly posted, “I’m going in.” NBC News reported that the gunman made a specific threat against Jews in the hours leading up to the attack.

This prejudice and harassment have long roots in American history. The United States Holocaust Memorial Museum describes World War I as a turning point that helped usher anti-Semitism from the far-right fringes of society into the mainstream. The ADL was founded in 1913 and early on pushed to revise a U.S. Army training manual that claimed Jews were “more apt to malinger than the native born.” After the war and the Russian Revolution that brought communism to power, many Americans blamed Jews for Bolshevism, just as some Germans, including Adolf Hitler, tried to blame domestic Jews for their nation’s loss in the First World War. Red scares linked Judaism and communism. In the United States, Jews were among the groups discriminated against in aspects of public life, such as hotel accommodations.