A federal law enforcement source said the incident did not appear to be an act of organized terrorism.
Six people, including the two shooters, three civilians and a police officer, died in a series of events that ended in a police shootout on Tuesday in Jersey City, New Jersey, across the Hudson River from New York City.
The four-hour gun battle at the Jewish JC Kosher Supermarket erupted after the pair shot the police officer at a nearby cemetery and then fled in a white van. It ended after police crashed an armored vehicle through the wall of the market.
"We are not in the position at this time to say definitively why the suspects stopped in front of the supermarket and began firing," New Jersey Attorney General Gurbir Grewal told a news conference.