The two shooters were fueled by hatred of Jews and police, New Jersey Attorney General Gurbir Grewal said at a press conference Thursday.
"We believe the suspects held views that reflected hatred of the Jewish people as well as hatred of law enforcement," Grewal said.
Investigators have identified several social media accounts they believe were used by the two shooters, David Anderson, 47, and Francine Graham, 50. Officials are working to determine the authenticity of the accounts as well as how the shooters chose their targets.
Grewal said there is evidence the shooters expressed interest in the Black Hebrew Israelites — a black separatist group that has been designated as a hate group by the Southern Poverty Law Center, largely due to the group's anti-Semitic rhetoric — but there is no evidence to suggest they were members of the group or of any other organization.
"We believe the two shooters were acting on their own," Grewal added.
BuzzFeed News has identified a number of social media accounts that appear to belong to Anderson in which he posted anti-police and anti-Semitic content and identified himself as a member of the Black Hebrew Israelite movement.
From 2010 until 2016, when he apparently dropped off the internet, Anderson purportedly created at least four different profiles on various social networks under different names, among them “Napoleon Hill,” “Baryon Bloodbourne,” “Kheayvan Brown,” and “Dawada Maqabath.”
In 2016, the Maqabath account posted a screed against Jews in the comments of a YouTube video.
Shortly before Tuesday's attack, the two shooters killed a police officer, Detective Joseph Seals, at a cemetery. Officials believe Seals was attempting to engage the two armed suspects before he was killed.
After that, they drove about a mile to the JC Kosher Supermarket, where they "immediately began shooting."
Mindy Ferencz, 31, Moshe Deutsch, 24, and Douglas Miguel Rodriguez, 49, were killed in the store. A fourth person was wounded but escaped and is "recovering fully."
Officials said the attack could have been even more deadly had police not intervened as quickly as they did. In addition to numerous firearms, police also recovered a pipe bomb from the shooters' van.
“They had a tremendous amount of firepower,” Grewal said.
The two shooters are also the prime suspects in the killing of another man — 34-year-old Michael Rumberger, who was found beaten to death in the trunk of a car in Bayonne, New Jersey, on Saturday.
Several elected officials have already called the shooting an act of domestic terrorism rooted in anti-Semitism.
"There's no question that this is a hate crime, and anti-Semitism should be called out aggressively and firmly and immediately for what it is," Jersey City Mayor Steven Fulop said Wednesday.
New York City Mayor Bill de Blasio also called the shooting an "act of terror" and a "premeditated, violent, anti-Semitic hate crime."
"We feel a lot of pain but we have to understand why this is a moment of urgency." de Blasio said. "This confirms a sad truth — there is a crisis of anti-Semitism gripping this nation; there is a crisis of anti-Semitism gripping this city. It has continued to take on a more and more violent form all over this country."