JERSEY CITY, New Jersey (WABC) -- The two attackers who authorities say killed a police officer and three civilians inside a grocery store in Jersey City are the prime suspects in the death of a man whose body had been found in a car trunk nearby over the weekend.
Attorney General Gurbir Grewal said David Anderson and Francine Graham are believed to be behind the murder of 34-year-old livery driver Michael Rumberger, who was found dead Saturday with head trauma in the trunk of a Lincoln Town Car.
But Grewal did not say what, if anything, linked Saturday's crime to Tuesday's shooting.
Rumberger was an employee at Grove Taxi & Airport Limo on Grand Street in Jersey City, working as a dispatcher and driver.
"They keep referring to him as 'just a cab driver,'" friend Yiesena Nunez said. "He wasn't just a cab driver. He was a man, a father of two girls. He wasn't a street thug. He wasn't out here doing drugs. He was a wonderful guy."
On Saturday night, he apparently picked up the wrong passengers. Police have confirmed that one of the weapons recovered in Jersey City was the one used to kill Rumberger.
But with the gunmen dead, the family is frustrated they will never get the answers as to why they shot him.
RELATED: Rumberger's family sets up GoFundMe for funeral expenses.
"I'm just really upset the fact that they're not here and I can't get any answers to anything," Nunez said. "I just want answers as to why? I have my daughter. She's graduating high school now. He's not going to be around."
Related: What we know about the suspects
Just before 10 p.m., members of the Bayonne Police Department responded to the area of 17th Street and John F. Kennedy Boulevard in Bayonne on a report of possible criminal activity. Upon arrival, they found Rumberger's body.
Friends say he knew his job was dangerous.
"I'm very sure he worried about that, but it's his job," Nestor Sorrano said. "That was his way of putting food on the table for the family."
Law enforcement sources said Detective Joseph Seals, who the suspects allegedly killed in Bay View Cemetery prior to the standoff at the Jewish grocery store, may have been interested in them as part of the Rumberger investigation.
Related: What we know about Detective Joseph Seals
At this point, the leading theory is the detective had a prior source relationship with one of the suspects, which may explain why he felt comfortable meeting in the cemetery without backup and without calling it in to others.
The killers then drove a stolen rental van over a mile to the JC Kosher Market, where they waged a drawn-out battle with police that filled the streets with the sound of high-powered rifle fire and turned the city into what looked like a war zone, with SWAT officers in full tactical gear swarming the neighborhood.
At the grocery store, police found five bodies -- the killers and three people who apparently happened to be there at the time.
The victims in the supermarket are 24-year-old Moshe Deutsch, 49-year-old Douglas Miguel Rodriguez, and 31-year-old Mindy Ferencz.
Related: What we know about victims inside Jewish market
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Jersey City shooting: Alleged attackers are suspects in earlier killing