The arrest on May 30 by French Police of Mehdi Nemmouche in connection with the murder of three people at the Jewish Museum in Brussels did not calm anyone’s fears. Far from it: Nemmouche is a French-born Islamist who fought with al-Qaeda-affiliated rebels in Syria before allegedly returning to Europe to murder Jews, and his apprehension is sending shockwaves across the continent.

Intelligence and police officials from Ottawa to Berlin to Paris have been issuing warnings about native-born Muslims who, after going to Syria to try to bring down strongman Bashar Assad, are returning home as trained, motivated Islamist terrorists. Nemmouche has not yet been charged, and it is not clear whether the 29-year-old could have been carrying out orders from al-Qaeda, or if this is the action of a “lone wolf,” like Mohammad Merah, who killed seven people at a Jewish school in Toulouse in 2012.

Either way, the killings at the Brussels Jewish Museum represent another devastating blow to Europe’s already beleaguered Jewish communities. They are already reeling from a spike in hate crimes, estimates that 150 million of their neighbors harbor extreme anti-Israel and/or anti-Jewish views, and from European Parliament elections held in late May that French Prime Minister Manuel Valls called a “political earthquake.” Last Monday, the prime minister and his colleagues awoke to a France that handed Marine Le Pen’s “fascism with a pretty face”— National Front — a stunning victory. Her party won 25 percent of the vote for members of the European Parliament in France — nearly double the number cast for the country’s ruling Socialist Party.

The results of the pan-European elections should not be dismissed as only a protest vote over high unemployment, high taxes and recessions. For many voters, the ballot box gave them a chance to join Eurosceptics in rejecting what they perceive as the co-opting of their national identities by faceless bureaucrats sitting in Brussels.

But it is whom they chose to sit in the next Parliament that is deeply worrisome. There is a likely bloc of 50 to 60 seats that could include France’s National Front, Greece’s extremist Golden Dawn, Hungary’s Jobbik and — for the first time — a parliamentarian representing the German NPD, neo-Nazi party. In other words, political parties — some of whose core constituency is attracted by xenophobia, nativist nationalism, anti-immigrant rhetoric (especially against Muslims) and anti-Semitism — are now positioned to help shape European social, economic and foreign policies. On top of those are extreme leftist parties in Greece, animal rights parties that denigrate core practices of Judaism and Islam including shechitah — Jewish ritual slaughter — and the Five Star Party, Italy’s second largest, which is led by anti-Semitic Beppe Grillo. Will these newly elected parliamentarians join those seeking to douse the flames of intolerance, or will they choose to leverage their newfound political clout to become more effective social arsonists?

Europe’s immigrants and minorities are deeply and understandably shocked by these developments, but none more so than the already embattled Jewish communities.

Benjamin Albalas, head of the Central Board of Jewish Communities in Greece, reacting to the election, told The Jerusalem Post that “a great number of European citizens seem to have forgotten what happened during the Holocaust and World War II. Racism and anti-Semitism are again hitting Europe,” he said. “It is time for immediate action.”

My colleague at the Simon Wiesenthal Center, Efraim Zuroff, warns that the elections could be “the beginning of a new and very dangerous era in which openly fascist and anti-Semitic parties might attain entree into government coalitions, which would significantly change the current constellation of political power in such a way that could seriously jeopardize the future of European Jewish communities.”

What is happening in Europe is not only a loss of hope, but a loss of memory: about World War II, about the Holocaust, and about the dangers of totalitarian movements of both the left and right that dragged Europe down into a long, 20th-century twilight of the soul. Many of the younger generation have never been taught, and many of the older generation — who should know better — have willfully chosen to forget.

And now, added to this already toxic mix, is the specter of European-born, battle-hardened Islamist extremists returning to the Continent to attack soft Jewish targets.

Europe was home to 10.5 million Jews in 1914; today, there are 1.5 million. A Europe incapable of or unwilling to defeat Islamist terrorism; to address head-on resurgent anti-Semitism; and a Continent bereft of a coherent, inclusive democratic culture will soon have no room for even these few Jews who remain. That’s why, from Scandinavia to Western Europe, from Hungary to Ukraine, dramas are unfolding in Jewish homes, as families contemplate voting with their feet, relocating to Israel, the United States or “anywhere but here.”

Rabbi Abraham Cooper is associate Dean of the Simon Wiesenthal Center and Museum of Tolerance. Dr. Harold Brackman, a historian is a consultant to the Simon Wiesenthal Center.