JERSEY CITY, N.J. — The two killers who stormed a kosher market in Jersey City had apparently been followers of the Black Hebrew Israelites — a fringe group whose members have been known to rail against white people and Jews — and one of them had made anti-Semitic posts online, according to a law enforcement official briefed on the investigation.

In a news conference Thursday, New Jersey Attorney General Gurbir Grewal says authorities believe Tuesday’s rampage that left the killers and four victims dead was “fueled both by anti-Semitism and anti-law enforcement beliefs.”

Grewal said authorities are investigating the attack as an act of domestic terrorism. He said officials believe the attackers were acting on their own.

The FBI on Wednesday searched the Harlem headquarters of the Israelite Church of God in Jesus Christ, which is the formal name of the Black Hebrew group, according to the official, who was not authorized to discuss the case publicly and spoke on condition of anonymity.

“The why and the ideology and the motivation — that’s what we’re investigating,” New Jersey Attorney General Grewal said Wednesday, adding that authorities are trying to determine whether anyone else was involved.

Others, including Jersey City Mayor Steve Fulop, pronounced the bloodshed a hate crime against Jews, with Fulop saying surveillance video made it clear that the attackers targeted the Jewish market, slowly and deliberately driving up to the grocery store in a stolen rental van and immediately opening fire.

The attackers were identified as David N. Anderson, 47, and Francine Graham, 50 — both of them also prime suspects in the slaying of a livery driver found dead in a car trunk in nearby Bayonne over the weekend, Grewal said.

Anderson used a rifle in the grocery attack. The attorney general wouldn’t confirm if Graham also had a weapon when she followed Anderson into the market. Several weapons were recovered from the store.

The victims killed in the store were: Mindel Ferencz, 31, who with her husband owned the grocery; 24-year-old Moshe Deutsch, a rabbinical student from Brooklyn who was shopping there; and store employee Douglas Miguel Rodriguez, 49.

Members of New York’s ultra-Orthodox Jewish community gathered Wednesday night for funerals for Ferencz and Deutsch. Thousands of people, mostly men, followed Ferencz’s casket through the streets of Brooklyn, hugging and crying.

The bloodshed in the city of 270,000 people across the Hudson River from New York City began at a graveyard, where Detective Joseph Seals, a 40-year-old member of a unit devoted to taking illegal weapons off the street, was gunned down by the assailants, authorities said. They then drove the van about a mile to the kosher market.

The drawn-out gunbattle with police filled the streets with the sound of high-powered rifle fire, as SWAT officers in full tactical gear swarmed the neighborhood. During the shootout, police used an armored vehicle to ram the store entrance.

The prospect of attacks against Jews weighed heavily on the more than 300 people who attended a vigil Wednesday night at a synagogue about a mile from where the shootings took place.

In the deadliest attack on Jews in U.S. history, 11 people were killed in an October 2018 shooting at a synagogue in Pittsburgh. Last April, a gunman opened fire at a synagogue near San Diego, killing a woman and wounding a rabbi and two others.

The kosher grocery is a central fixture in a growing community of Orthodox Jews who have been moving to Jersey City in recent years and settling in what was a mostly black section of Jersey City, causing some resentment.

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Sisak reported from New York. Associated Press writers Jim Mustian in New York and Mike Catalini in Trenton, New Jersey, contributed.