The man and woman who killed four people in Jersey City last month in a hate-filled assault on a kosher market had broader plans to sow violence and fear in New Jersey’s Jewish community and harbored hatred toward police, authorities said Monday.

An explosive device that had the capacity to kill or injure people up to 500 yards away was found in van of the suspects, authorities said.

David Anderson, 47, and Francine Graham, 50, prepared for months before carrying out the attack, which included the killing of a Jersey City police detective on Dec. 10 followed by a rampage at a kosher grocery store that took the lives of three civilians, authorities said. Anderson and Graham were killed in a shootout with police at the Jersey City market.

Fueled by a radical ideology loosely affiliated with the Black Hebrew Israelites, the pair purchased a cache of weapons and trained to use them in Ohio, authorities said. Before the Jersey City attack, they researched another attack on a Jewish community center in Bayonne, officials said.

State and federal authorities disclosed new details of their ongoing investigation Monday, one month after the horrific spree of violence, saying that they are confident Anderson and Graham were motivated by hatred of Jews and law enforcement. U.S. Attorney Craig Carpenito described the Jersey City attacks as “profoundly un-American” and a “senseless, evil and cowardly act,” but said the broader plan was thwarted.

“We know now that they planned greater acts of mayhem on both communities,” he said.

Video from inside the kosher supermarket captured Anderson saying: “They stole our heritage, they stole our birthright, and they hired these guys to stop us,” Carpenito said.

Authorities also provided more information on what happened at the Bayview Cemetery where Jersey City detective Joseph Seals was killed shortly before the attack on the grocery story.

Seals, who had gone to the Bayview Cemetery to meet with a man whose vehicle had been impounded in an unrelated matter, apparently had a chance encounter with Anderson and Graham.

“He was just there doing his job,” Carpenito said Monday.

Authorities said they aren’t sure what prompted the interaction, but Carpenito said a notice had been issued for officers to be on the lookout for a U-Haul van, like the one Anderson and Graham had rented. He said investigators have speculated that is why Seals approached the pair.

Carpenito said the detective’s interaction with Anderson and Graham threw them off of their “broader plan” of potentially more violence.

An explosive device found in the U-Haul van Anderson and Graham had rented could have killed or injured people up to five football fields, or 500 yards, away, said FBI special agent in charge Greg Ehrie. The two also had enough materials to construct a second deadly explosive device, but Ehrie said it may never be known what they intended.

“The entire truth lies with the two dead attackers,” Ehrie said.

U.S. Attorney Craig Carpenito (center) speaks at a press conference on on Monday at the FBI Headquarters in Newark to provide an update on Jersey City mass shooting. Supporting Carpenito are (L-R) State Police Lt. Col. Fritz Fragé, N.J. Office of Homeland Security Director Jared Maples, Attorney General Gurbir Grewal and FBI Special Agent in Charge Gregory Ehrie.Steve Hockstein | For NJ Advance Media

Surveillance video showed Anderson and Graham, both wearing tactical gear and armed with a total of five firearms, arrive outside of the kosher grocery store in Jersey City’s Greenville neighborhood after they had killed Seals in the cemetery, authorities said. The video shows them shooting as they moved into the store. Inside, the two killed Mindel Ferencz, 33, who owned the store, Moshe Deutsch, 24, of Brooklyn and Miguel Douglas Rodriguez, 47, who worked at the store.

Authorities said they recovered five guns inside the store, including a “possibly self-manufactured” AR-15-style weapon believed to be used by Anderson and a Mossberg 12-gauge shotgun that Graham was carrying.

Investigators also found at least two handwritten notes in the Anderson’s pockets.

One note read: “FBIs war on black America 35:45,” referencing the title of a 1990 documentary and a moment in the film, in which Fred Hampton, the Black Panther leader, describes law enforcement officers as “fascist pig cops.” The other note had the phone number of a Keyport man who was charged with illegally possessing 12 firearms after FBI agents interviewed him a few days after the attack.

In the U-Haul van, authorities found a pipe bomb and a note that read: “I do this because my creator makes me do this and I hate who he hates,” law enforcement sources told the New York Post, and later confirmed by others close to the investigation.

Authorities confirmed Monday that Anderson and Graham were suspects in two other incidents leading up to the deadly Jersey City attack.

A week before, on Dec. 3, two shots were fired at a vehicle driven by a person clearly identified as of the Jewish faith, Carpenito said, on Route 1 and 9 near Newark and Elizabeth. The rear window was shot out and no one was injured. Investigators determined Graham’s phone was in the area at the time of the shooting, and the ballistics matched a gun linked to the pair, authorities said.

Days later, on Dec. 7, authorities said Anderson and Graham killed Michael Rumberger, a Bayonne taxi driver by bludgeoning him and then shooting him in the head. They left Rumberger’s body in the trunk of the Lincoln Town Car he was driving.

Officials said Monday that Rumberger’s blood was found on a bible that belonged to the attackers and that his DNA was on their clothes and at least one weapon.

Carpenito said he could not say if Rumberger was targeted, but he said Anderson and Graham Googled the meaning of the surname “Rumberger” after killing the 34-year-old.

Ehrie, the FBI agent, said Anderson and Graham were not on the radar of law enforcement before the Jersey City shooting.

Anderson, who served in the Army reserves, had a lengthy criminal record for a number of gun charges and served time in prison. He met Graham in 2017, and neighbors of the woman said she began to change after her relationship with Anderson began.

Drake Serge, who lived next door to Graham in an Elizabeth housing development, said after Graham met Anderson, "everything went downhill from there.”

Authorities said one of the guns used in the shooting were purchased legally in Ohio by Graham in 2018. As a convicted felon, Anderson could not legally purchase a firearm.

Staff writers Ted Sherman, S.P. Sullivan and Sophie Nieto-Munoz contributed to this story.

Joe Atmonavage may be reached at jatmonavage@njadvancemedia.com. Follow on Twitter @monavage.

Blake Nelson can be reached at bnelson@njadvancemedia.com. Follow him on Twitter at @BCunninghamN.

Have a tip? Tell us. nj.com/tips.

Get the latest updates right in your inbox. Subscribe to NJ.com’s newsletters.