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The man and the woman who gunned down a New Jersey police officer and three bystanders inside a kosher market last month were carrying explosives that could have led to even more deaths, authorities said Monday.

Francine Graham and David Anderson had a bomb in their van and could have harmed people up to five football fields away, had they not been killed in a shootout and standoff with police Dec. 10, U.S. Attorney Craig Carpenito said.

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New Jersey's top federal law enforcement official said the killing of Graham and Anderson “probably saved dozen, if not more, lives.”

"We further confirm that this was, in fact, a hate crime and episode of domestic terrorism," Carpenito said.

Emergency responders survey the scene at a kosher supermarket where gunmen killed several people the day before in Jersey City, N.J., on Dec. 11, 2019. Seth Wenig / AP

It wasn't revealed what targets Graham and Anderson might have been considering, but Carpenito said they had done research on a Jewish community center in Bayonne.

The bloodshed began that day when Jersey City police Detective Joseph Seals was killed after he approached Graham and Anderson in connection with a livery cab driver's slaying the prior weekend, officials have said.

The duo then made their way to the JC Kosher Supermarket on Martin Luther King Boulevard during what officials have described as a hate-fueled terror spree.

Those killed inside the store were Mindy Ferencz, 31, Douglas "Miguel" Rodriguez, 49, and Moshe Deutsch, 24.

Ferencz ran JC Kosher Supermarket with her husband. Rodriguez, an immigrant from Ecuador, has been hailed as a hero for ushering customers to safety before he was killed.