Authorities say the two people who stormed a kosher grocery in Jersey City and killed three people had a bomb powerful enough to kill or injure others from “five football fields away.”

Officials said Monday that David Anderson and Francine Graham planned an assault for some time and were involved in another shooting targeting a Jewish person a week earlier.

“On Dec. 3, we now know that there was a shooting. Two shots were fired into a vehicle driven by someone who was visibly of the Jewish faith, on Route 1&9 in or around the Newark/Elizabeth area,” said U.S. Attorney Craig Carpenito.

The driver was not hurt, but Carpenito said that the bullets destroyed the back window of the car. The victim did not report the shooting until after the grocery store attack.

Carpenito said that Graham’s phone pinged near the area of the shooting, around the time of the shooting. And he said ballistics found in the victim’s car matched the .22-caliber gun that was used in the murder of Michael Rumberger, a taxi driver allegedly killed by Anderson and Graham on Dec. 7.

Carpenito says that the gun used in both shootings was later recovered at the scene of the Dec. 10 attack at the JC Kosher supermarket.

State and federal authorities say that the attackers were fueled by hatred of Jews and law enforcement that they expressed in notes and online postings. Before the killings at the grocery store, they had killed Jersey City Police Detective Joseph Seals.

“We have reviewed video evidence of Graham and Anderson conducting target practice with long guns in Austintown, Ohio,” Carpenito said.

The pair also bought five guns while in Ohio, one of which was recovered at the scene of the attack. The pair were killed during a long siege with police officers.

The Associated Press wire services contributed to this report.