PARIS — Every morning, in a part of the 11th Arrondissement of Paris that has not yet gentrified, Mireille Knoll would sit at home watching television as she waited for her personal care aide.

The aide, Leila Dessante, would clean the small second-floor apartment, cook lunch and keep company with Ms. Knoll, a 85-year-old grandmother and Holocaust survivor. “She would take my face in between her hands and always ask, ‘How are you doing today, sweetheart?’” Ms. Dessante recalled on Wednesday.

Ms. Knoll’s gentle routine was brutally interrupted last week when she was killed in her apartment. The attack shocked her neighbors, France’s Jewish community and the country as a whole. Two suspects, men in their 20s, have been placed under formal investigation on charges of murder with an anti-Semitic motive.

The killing has raised questions about a persistent strain of anti-Semitism in France, “an anti-Semitism that remains, that transforms, that reappears, that mutates,” according to Édouard Philippe, the prime minister.