JERSEY CITY, New Jersey (WABC) -- The investigation continues into the deadly shooting and standoff in Jersey City that left a police officer and three civilians dead, and part of the focus is now on a fringe group with anti-Semitic, anti-white and anti-police tendencies that the now-deceased suspects were said to follow.
The alleged killers were identified as 47-year-old David Anderson and 50-year-old Francine Graham and were believed to be followers of the Black Hebrew Israelites.
New Jersey Attorney General Gurbir Grewal has not officially called the incident a bias attack, but he said Thursday that the evidence is strongly pointing towards hate as a motive. He also said it is being investigated as domestic terrorism fueled by anti-Semitic and anti-police beliefs.
Five firearms have been recovered linked to Anderson and Graham, including an AR-15-style weapon, a 12-gauge shotgun, a 9-mm semiautomatic weapon, a 9-mm Glock 17, and a .22 caliber Ruger Mark 4 with a silencer. Four weapons were found inside the JC Kosher Supermarket on Martin Luther King Drive, while the Ruger was located inside the stolen U-Haul van the suspects drove to the scene.
Through serial numbers, authorities were able to trace two of them to separate gun shops in Ohio, where Graham reportedly purchased them.
Related: What we know about the suspects
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.
Authorities said Thursday that while both suspects showed interest in the group, they have not been formally linked to the Black Hebrew Israelites or any other organization.
The officer killed was identified as Detective Joseph Seals, a husband and father of five who had been with the department since 2006, while the victims in the supermarket are 24-year-old Moshe Deutsch, 49-year-old Douglas Miguel Rodriguez, and 31-year-old Mindy Ferencz.
Related: What we know about victims inside Jewish market
Authorities said a device found in the back of the U-Haul proved to be an operable explosive device, a pipe bomb. Also in the U-Haul were notes with religious writings, one of which included the quote, "I do this because my creator makes me do this and I hate who he hates," according to multiple law enforcement sources.
Authorities in New Jersey reportedly did not have the Black Hebrew Israelites on their radar as a violent group, considered more a nuisance at public events.
Related: NJ crime data shows increase in Jersey City hate crimes
The bomb squad detonated the device, though it remains unclear what the suspects had planned to do with it.
The incident began at the Bay View Cemetery, where Seals was fatally shot and another officer wounded in the shoulder.
Related: What we know about Detective Joseph Seals
Officials say Anderson and Graham then drove the U-Haul about a mile to the grocery store, parking across the street and exiting the vehicle with guns drawn. They immediately began firing, shooting four people inside, one of whom managed to flee from the scene.
Officers in the area quickly arrived on scene, trapping the two suspects inside. The lengthy gun battle then commenced.
As the suspects fired upon them from inside the grocery store, police retreated and took up defensive positions as hundreds of officers, SWAT units, and the Bureau of Alcohol, Tobacco, Firearms and Explosives, and the FBI descended on the area.
Related: The scene on the streets of Jersey City captured in video and photos
Two other officers were wounded but were later released from the hospital, authorities said. They were identified as Mariela Fernandez and Ray Sanchez
Jersey City Mayor Steven Fulop said Wednesday morning that the gunmen clearly targeted the market, with surveillance video showing them driving slowly through the city's streets before stopping outside, calmly exiting their van and immediately opening fire. Grewal said Thursday that investigators were working to determine how the suspects chose their target, as well as detail their interaction with Seals.
Law enforcement sources said Detective Seals may have been interested in the two suspects who ultimately killed him because of a weekend homicide in Bayonne, where a Jersey City man identified as Michael Rumberger was found in the trunk of a Lincoln Town Car on Saturday night.
That crime had not been immediately solved.
At this point, the leading theory is the detective had a prior source relationship with one of the suspects, which may explain why he felt comfortable meeting in the cemetery without backup and without calling it in to others.
New Jersey Governor Phil Murphy ordered that the U.S. and New Jersey flags be flown at half-staff at all state buildings and facilities from December 13 through December 20 in honor of the victims of the shooting.
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Jersey City shooting: Attorney General says evidence points to hate crime