Officials are investigating the shootout in a kosher grocery in Jersey City, N.J., as a potential act of domestic terrorism, and recovered several hundred shell casings along with a cache of rifles and handguns from the scene, they said.

Law-enforcement officials said the assailants, David Anderson and Francine Graham, were armed with a 12-gauge shotgun, two .9mm handguns, a .22 caliber handgun outfitted with a homemade silencer and an AR-15-style weapon, a rifle that has been used in many mass shootings. Ms. Graham legally purchased the shotgun and the .22 caliber handgun in Ohio in spring 2018, officials said at a press conference Thursday.

Investigators were still determining why the shooters chose to attack the Jersey City Kosher Supermarket, where three people were killed, including two Hasidic Jews. But recent interviews with witnesses and other evidence indicated that the assailants, who died Tuesday following an hourslong shootout with police, held views that reflected hatred of Jews and police officers, said New Jersey Attorney General Gurbir Grewal.

“The evidence points towards acts of hate,” Mr. Grewal said. “I can confirm that we are investigating this matter as potential acts of domestic terrorism, fueled both by anti-Semitism and anti-law-enforcement beliefs.”

Mr. Grewal confirmed that a note was recovered from the stolen U-Haul van used by the shooters, but declined to discuss what it said. Law-enforcement officials have also identified a number of social-media accounts that may have been used by the shooters, which investigators are trying to confirm, he said.