The broader plot was thwarted, Mr. Carpenito added, by the intervention of Joseph Seals, a Jersey City police detective who was fatally shot by Mr. Anderson and Ms. Graham in a cemetery about a mile from the kosher market.

Detective Seals, officials said, was in the cemetery to meet with a man about the potential return of a vehicle that the Jersey City police had impounded.

In the Dec. 3 shooting, a man, described as “visibly Jewish” by officials, was driving on Routes 1 and 9 near Newark and Elizabeth when two shots were fired at his car, they said. No one was injured, but the rear window was shot out, officials said.

The driver of the car did not immediately report the shooting to the authorities, said Rabbi Jack Meyer, the president of Misaskim, a nonprofit Jewish organization.

But several days after the Jersey City attack, Mr. Meyer said, the man “put two and two together” and contacted him. The man told Mr. Meyer that he was on his way to work at about 9:45 a.m. when he saw a U-Haul van ahead of him on the highway.

Moments later, Mr. Meyer said, a bullet flew through the driver side window. Mr. Meyer said he had put the man in touch with the authorities.

Ballistics tests showed that the bullet had come from a .22-caliber handgun found in the rental van used by Mr. Anderson and Ms. Graham on Dec. 10, officials said. Cellphone records also indicated that Ms. Graham’s phone was in the area where the highway shooting occurred around the time it happened, officials said.

Officials had previously identified Mr. Anderson and Ms. Graham as the leading suspects in the killing of a taxi driver who was found dead in the trunk of a Lincoln Town Car in Bayonne on Dec. 7, officials said.

On Monday, officials said that ballistics tests had linked the same .22-caliber handgun used in the highway shooting to the death of cabby, who was bludgeoned and shot in the head.

The authorities also tied Mr. Anderson and Ms. Graham to the taxi driver’s killing with other evidence. His blood was on a Bible found in the rental van and his DNA was on clothing found there, officials said.

The authorities also disclosed that Mr. Anderson and Ms. Graham had searched online at various points in December for information about a Jewish community center in Bayonne, about cab companies in Jersey City and about whether a car door would stop a bullet fired at an angle.

Officials said they had uncovered surveillance video that showed the two taking target practice with long guns in Austintown, Ohio, on Dec. 1.

Also, officials said, one of two notes found in Mr. Anderson’s pockets after he and Ms. Graham were killed in a standoff with the police on Dec. 10, read, “FBIs war on black America 35:45,” a reference to a 1990 documentary in which the Black Panther leader Fred Hampton describes law enforcement officers as “fascist pig cops.”

The second note had the phone number of a Keyport, N.J., man who was later charged with illegally possessing guns.

Video from inside the market before Mr. Anderson was killed, Mr. Carpenito said, captured him saying, “They stole our heritage, they stole our birthright, and they hired these guys to stop us.”

Other footage showed the rental van appearing to scout the market several times in the week leading up to the attack, the last time about an hour and a half before the first calls about it came in.