St. Petersburg police arrested a suspect in the murder of a Jewish schoolteacher that authorities said was motivated by jealousy. Dmitri Nikulinsky, 22, a teacher and biology student at a Chabad-run school, was stabbed to death Saturday in what some thought was an anti-Semitic attack. Berel Lazar, one of Russia’s two chief rabbis, told Interfax on Sunday that “the information available for now breeds serious suspicions that the crime was ethnically motivated.” On Monday, St. Petersburg police detained Georgiy Kulik for the crime, citing jealousy, not anti-Semitism, as the motive.Nikulinsky’s mother found him outside his home Saturday morning; he had been stabbed repeatedly in the neck. Police told community leaders that Kulik, 26, had seen Nikulinsky escorting home Kulik’s ex-girlfriend the preceding evening, and that he had returned to kill Nikulinsky in a jealous rage. But community leaders are unconvinced. “I think it’s still early to say that it’s not an act of anti-Semitism or ethnically motivated violence,” St. Petersburg’s chief rabbi, Mendel Pevzner, told JTA on Monday. Police are scheduled to meet with St. Petersburg community leaders later Monday to discuss the case.