The slain officer was identified as Joseph Seals, a 17-year department veteran and father of five -- including a newborn -- who lived in North Arlington.
“Our thoughts and prayers are with Joe’s family during this Christmas season and beyond,” Jersey City Mayor Steven Fulop said.
“We take for granted sometimes the selfless work a police officer does when they wear that uniform. In the end they are people that volunteered to keep everyone else safe regardless of the circumstance," the mayor said in a statement.
"Today we tragically lost Joe as he was serving the [people] of Jersey City that he volunteered to serve," Fulop added. "I know I speak for all the residents that we are grateful for all he has done for our city. Rest In Peace.”
Two other police officers who were wounded were expected to survive, Hudson County Prosecutor Esther Suarez said after the incident had finally ended Tuesday afternoon.
Squads of law enforcement units converged on a barricaded Jersey City kosher grocery store, where responders said five bodies were found following a gun battle that began hours earlier and involved what witnesses said were hundreds of shots.
Newark Police Detective Joseph Kerik, the son of former NYPD Commissioner Bernard Kerik, was one of three officers who rushed the store and gunned down the assailants.
HEROES: Former NYPD Commissioner Kerik's Son Among Trio That Killed Jersey City Shooters
A pipe bomb was also found, authorities said.
“We have no inkling what the motive was yet,” Jersey City Police Chief Michael Kelly said. "Our officers were under fire for hours."
Fulop, however, said he believed the shooters targeted the JC Kosher Supermarket in the city's Greenville section.
"Due to an excess of caution the community may see additional police resources in the days/weeks ahead," he tweeted Tuesday night. "We have no indication there are any further threats."
Seals, 40, was shot in the head at nearby Bayview Cemetery shortly before 12:30 p.m., authorities confirmed. He was the 35th Jersey City police officer killed in the line of duty in the department's history.
Another officer was shot in the shoulder in the predominantly Jewish neighborhood on Martin Luther King Drive near Bayview Avenue.
A massive assemblage of law enforcement units rushed to the store, which neighbors said is next to a building that houses a shul and a Hassidic school with 40 children who all remained sheltered in place during the gunfight.
Also locked down was Sacred Heart School, a Catholic elementary school across the street.
Several other city schools also were locked down, area buses and trains were halted, and Exit 14B of the New Jersey Turnpike exit was temporarily closed.
Two assailants -- a man and woman -- had fled to the store after the shooting, which authorities said occurred while Seals was investigating the killing of a city man found in the trunk of a car in Bayonne.
SEE: Authorities ID Man Found Dead In Bayonne Car Trunk
The pair barricaded themselves inside the store and began randomly firing what witnesses said were long rifles.
Authorities believe the shooters killed the civilians inside -- all Jews, at least one of whom worked there.
A SWAT team and city Emergency Services Unit were immediately summoned. Gunfire could be heard as officers communicated on their radios.
SEE VIDEO: HudsonTV.com
New Jersey State Police, as well as the FBI and ATF, also responded, along with Bergen County's Crisis Negotiations Team, a Bergen County Regional SWAT team and the Hudson County Sheriff's Office.
The NYPD and Paramus and Garfield police also sent their Emergency Services units.
Statement from New Jersey Attorney General Gurbir S. Grewal:
"We stand with Jersey City as we mourn today’s terrible tragedy. The Attorney General’s Office is leading the criminal investigation and any public statements about the matter will be issued by our office. We continue to work closely with our federal, county, and local partners and we remain grateful for the outpouring of support from law enforcement across the region and the nation. We recognize the fear that communities rightfully feel after traumatic incidents such as these, and we are committed to providing all resources necessary to ensure the safety and well-being of our fellow residents."
Click here to follow Daily Voice Cresskill-Closter and receive free news updates.