This year as last, the Jewish community in France will spend Passover in the shadow of the brutal murder of a vulnerable, elderly Jewish woman living on her own in public housing. She survived the Holocaust, but not a murderer in Paris.

Marchers honor the memory of Holocaust survivor Mireille Knoll, 85, who was murdered last week in a brutal anti-Semitic attack. Credit: European Jewish Press.

On March 23, 85-year-old Mireille Knoll was stabbed to death and her apartment set on fire by two intruders, one of whom is alleged to have shouted the words “Allahu Akhbar” before plunging the weapon into his victim. Last year, on April 4, 65-year-old Dr. Sarah Halimi was badly beaten and then ejected from the window of her third-floor apartment by an intruder, a young Malian-born Islamist, who bellowed the word “Satan” at his victim during the ordeal.

There are some obvious similarities between these two atrocities. Both Dr. Halimi and Mrs. Knoll had close family nearby, but they lived alone. Both of them resided in the 11th arrondissement in eastern Paris, where many other elderly Jews in similar circumstances remain among a much larger community of Muslims from the Maghreb and West Africa. Indeed, residents in the neighborhood told a Paris TV station after Mrs. Knoll’s murder that they live in fear.

“We have to hide the signs of our Judaism—kipot, Magen David necklaces,” said Mickaël, who has lived there for 15 years. “We trim our beards short, and we don’t wear our tzitzit on the outside.” A Jewish shopkeeper confessed that he was forced to keep his door locked most of the time. “There are many suspicious people trying to get in,” he explained. “We’ll see what the future brings.”

But there is also a major difference between the two murders. Dr. Halimi’s death was barely noticed for weeks and months by the media in France and abroad. But Mrs. Knoll’s death—and the ensuing demonstration against anti-Semitism less than a week later that brought a crowd of nearly 30,000 onto the streets of Paris—has been front-page news for The New York Times, The Washington Post, the BBC and every single media outlet in France.

In Dr. Halimi’s case, several French officials scandalously tried to deny the anti-Semitic nature of her murder on the grounds of her assailants’ supposed mental illness, despite the fact that he is a known petty criminal who growled the words “dirty Jewess” when passing Dr. Halimi on the stairwell. In Mrs. Knoll’s case, there has been no such dispute, and the two suspects arrested for her killing have already been charged with an anti-Semitic hate crime.

Why the contrast? Perhaps the most significant factor here, tragically, is timing. When Dr. Halimi was murdered, the French elections were a few weeks away and a good portion of the French media decided, with characteristic hubris, that reporting her ordeal would boost the fortunes of the far-right presidential candidate, Marine Le Pen. So for weeks, virtually nothing was said about a murder notable for its chilling level of violence, as well as the incompetent response of the police and judicial authorities; “I waited seven weeks before I said anything,” Dr. Halimi’s brother, William Attal, later grieved.

The decisive victory over by Le Pen by centrist candidate Emmanuel Macron in May 2017 was therefore the most important outside development upon the Halimi case—and in many ways, explains the radically different response to Mrs. Knoll’s fate.

Within weeks of his election, Macron solemnly recognized that Dr. Halimi had been a victim of anti-Semitic hatred. Since then, the French president has frequently attacked French anti-Semitism and Islamist anti-Semitism, has spotlighted the thematic overlaps between anti-Semitism and anti-Zionism, and has declared his solidarity with the country’s 465,000-strong Jewish community—pointing out, as have many others, that such a modest number belies the true nature of the Jewish contribution to France over the past millennium.

This was the changed environment into which the news of Mrs. Knoll’s murder emerged last week. Her killing took place on the same day that a heroic police officer and three hostages were shot dead by an Islamist terrorist during a siege at a supermarket in southern France. And when Macron delivered his speech at the moving national tribute on Tuesday to Col. Arnaud Beltrame, the slain gendarme, he noted that Mrs. Knoll—“murdered because she was Jewish”—was a victim of the same “barbaric obscurantism.”

As historically significant as these statements certainly are, the situation is akin to the shattering late discovery by investigators that a series of previously unlinked murders were actually committed by the same person. Since 2006, when the young cell-phone salesman Ilan Halimi was kidnapped and murdered by a largely Muslim gang who seized him on the conviction that “all Jews are rich,” France has witnessed hundreds of assaults and home robberies alongside these shameful murders of Jews. In the end, it took the slaying of a woman who survived the July 1942 “Vel d’Hiv” Nazi deportation of the Jews of Paris—the widow of a survivor of Auschwitz no less—to identify anti-Semitism as the serial killer responsible for all these crimes of hate. Those who admit grimly that this represents a form of progress are probably right.

Ben Cohen writes a weekly column for JNS on Jewish affairs and Middle Eastern politics. His writings have been published in Commentary, the New York Post, Haaretz, The Wall Street Journal and many other publications.