The two attackers who killed a police officer and three civilians in a Jewish Orthodox community in Jersey City on Tuesday are also prime suspects in the murder of an Uber driver earlier in the week, New Jersey Attorney General Gurbir Grewal said at a press conference Wednesday.

The suspects were identified as 47-year-old David N. Anderson and 50-year-old Francine Graham, who are both deceased. Grewal said Anderson and Graham are suspected to have also murdered an Uber driver in Bayonne, New Jersey, on Saturday.

The driver, 34-year-old Michael Rumberger, was found in the trunk of a Lincoln Town Car with head injuries and was pronounced dead at the scene, prosecutors said, according to The Associated Press. Grewal did not share why the attackers are considered prime suspects in Rumberger's murder.

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The gunfire began at the Bay View Cemetery in Jersey City, where police confronted the suspects. Jersey City Police Officer Joseph Seals was killed at the cemetery, Grewal said.

According to the Attorney General, the suspects then parked a white U-Haul van directly across the street from a Kosher supermarket at approximately 12:21 p.m. ET on Tuesday, about a mile away from the cemetery. Within seconds of arriving, Anderson got out of the van with a rifle in hand, walked towards the market and began shooting, Grewal said.

Graham, who was the passenger in the van, then followed Anderson into the store. The suspects began shooting almost immediately upon entering the supermarket, Grewal said. Inside the supermarket were four civilians, three of whom died in the attack. The deceased victims have been identified as 31-year-old Mindel Ferencz, 49-year-old Douglas Miguel Rodríguez, and 24-year-old Moshe Deutsch.

A fourth civilian in the store was shot, but was able to escape at the beginning of the attack, according to Grewal. That person's name has not been released.

After an hours-long standoff with police, in which a police armored vehicle broke through the front of the supermarket, the attack ended with the suspects' deaths, according to the attorney general. "We've recovered numerous firearms from the scene ... we also recovered a pipe bomb," Grewal said. The bomb was found in the attackers' van, FBI agent Gregory Ehrie said.

"It was a viable device, meaning it could be a device that would have exploded," Ehrie said. "... Not complicated, but sophisticated in the sense that time and effort went into creating it."

Authorities are still working to understand the motive for the attack, and whether there were any other people involved, but Grewal said authorities have obtained "digital and documentary evidence" that they are currently reviewing.