BAGNEUX, France — She could not stop thinking about Ilan Halimi.
And when Marie-Beatrice thought about the young Jewish man tortured to death by her neighbors during 24 days of squalid captivity in the basement a few floors below her apartment, she could not stop crying.
"I try not to blame myself, but I can't avoid it," said the weary 46-year-old, wrapped in a purple bathrobe after work Friday. "It happened next door, and I can't believe it happened. I would want to tell Ilan that if we'd heard his suffering, we would have reported it. I tell myself that Ilan surely must have thought there was noise, people lived upstairs. And he hoped someone would hear. I imagine him in the boiler room, and I want to ask him to forgive me."
Marie-Beatrice sat alone with her guilt in the aging, 11-story apartment block on Prokofiev Street in this working-class immigrant enclave on the southern edge of Paris. On a table was a summons from the police, who are canvassing neighbors to have them testify about anything they witnessed during Halimi's recent ordeal.
Marie-Beatrice, who asked that her last name not be used out of fear for her safety, said her housing project was relatively calm. But people steer clear of hoodlums and drug dealers who prowl cellars, garages and hallways -- urban no man's lands ruled by fear, silence and machismo.
At the entrance to her building, someone posted an accusatory newspaper headline proclaiming that the neighborhood had refused to see the evil within: "They knew."
Marie-Beatrice's building was a hide-out for a multiethnic gang that called itself the Barbarians. They kidnapped Halimi, a 23-year-old cellphone salesman, authorities say, because he was Jewish and they thought Jews were rich. They subjected his family and a rabbi to hundreds of abusive phone calls and e-mails demanding ransom.
But greed gave way to sadism in the makeshift dungeon guarded by cigarette-smoking youths. Halimi's captors beat, burned, stabbed and poured toxic fluid on him, prosecutors say. One youth snapped at Halimi that he didn't like Jews, and then stubbed out a cigarette on his face.
Halimi died soon after the gang dumped him, bound and naked, beside railroad tracks Feb. 13. No money had changed hands.
Police have made 15 arrests, tracking down the accused ringleader Thursday in the West Africa nation of Ivory Coast. Eleven suspects face charges of conspiracy, kidnapping and murder motivated by anti-Semitism. The case traumatized the Jewish community and was condemned by President Jacques Chirac, political parties across the spectrum and Muslim groups. Tens of thousands of people are expected to march today in Paris in Halimi's memory.
In a society recovering from recent riots in predominantly Muslim areas, the slaying forces new attention on anti-Semitism, which has played a role in French history.
Halimi's family and many others in the Jewish community are convinced that the atrocity was the result of religious hatred. Even among some Jewish leaders, however, questions persist.
Rather than a premeditated anti-Semitic murder, it seems a more complex result of dysfunction in the narrow world of thug culture: a poisonous mentality that designates Jews as enemies along with other "outsiders," according to investigators and other observers.
"They mix everything together; they are against Jews, Americans, France, the West," said Sammy Ghozlan, a retired police chief and activist who tries to combat anti-Semitism. "If they could have gotten their hands on a French cop in the same way, they probably would have done the same thing.... I don't think the violence in this case was the original purpose, it developed progressively."
In contrast with the riots, which mainly targeted property and the police, the killing resembled crimes of gratuitous cruelty that have occurred in the concrete badlands around Paris: gang rapes involving as many as 17 youths, women burned to death by spurned suitors, a visiting photographer beaten to death on the spot.
The Barbarians were driven by a tribal, predatory code that glorifies brutality, authorities say, a subculture nourished on violent films; rap music that curses France and politicians; Islamic fundamentalist literature; and jihadist videos. The photos that the kidnappers sent via e-mail of a bound, battered Halimi with a gun to his head resembled images of hostages and prisoners in Iraq, authorities say.
"There are only two idols in the projects today: [French NBA star] Tony Parker and Abu Musab Zarqawi," the leader of Al Qaeda in Iraq, said author Stephane Bartome, a former anti-terrorism detective. "And unless you're a really good basketball player, it's easier to emulate Zarqawi."