ABC News December 17, 2019

Grieving officers gather at funeral for slain Jersey City detective

WATCH: Grieving officers gather at funeral for slain Jersey City detective

A sea of blue filled a New Jersey church on a frigid, rainy Tuesday morning for the funeral of a Jersey City detective shot dead before a massive gun battle last week.

Officers on foot, horseback and motorcycles lined up along the street as Det. Joseph Seals' coffin, draped with the American flag, arrived at Jersey City’s Saint Aedan's Church.

Shannon Stapleton/Reuters
Police officers stand and salute as the casket is carried into the funeral service for Jersey City Police Detective Joseph Seals at St. Aedan's Church in Jersey City, N.J., Dec. 17, 2019.
Shannon Stapleton/Reuters
A police procession arrives at the funeral service for Jersey City Police Detective Joseph Seals at St. Aedan's Church in Jersey City, N.J., Dec. 17, 2019.

Every police department in New Jersey sent officers to join the thousands at the funeral, reported NJ.com.

Jersey City Mayor Steven Fulop said police departments from surrounding towns offered to help patrol Jersey City Tuesday so Seals' colleagues could attend the service.

Attorney General William Barr was also among those in attendance.

Shannon Stapleton/Reuters
Police officers gather on the street ahead of the funeral service for Jersey City Police Detective Joseph Seals at St. Aedan's Church in Jersey City, N.J., Dec. 17, 2019.
Seth Wenig/AP
Police officers and other first responders gather before the funeral of Jersey City Police Detective Joseph Seals in Jersey City, N.J., Dec. 17, 2019.

Seals, a plainclothes detective and married father of five, was the first victim of the Dec. 10 shootings.

Seals, 39, was killed at the Bay View Cemetery in Jersey City, allegedly by David Anderson and Francine Graham.

Seth Wenig/AP
A traffic jam of police cars is seen before the funeral of Jersey City Police Detective Joseph Seals in Jersey City, N.J., Dec. 17, 2019.
Shannon Stapleton/Reuters
New Jersey State Police officers stand in formation on the street ahead of the funeral service for Jersey City Police Detective Joseph Seals at St. Aedan's Church in Jersey City, N.J., Dec. 17, 2019.
(MORE: Jersey City Jewish deli killing to be investigated as domestic terrorism: Officials)

The two suspects -- armed with multiple guns -- then stormed the Jersey City Kosher Supermarket, about 1 mile from the cemetery, where they allegedly killed three others.

Anderson and Graham died in the market during an hours-long shootout with police.

The motivation behind Seals' murder and the market attack "clearly appears to be a bias towards both the Jewish community and law enforcement," said Craig Carpenito, U.S. attorney for the District of New Jersey.

Seth Wenig/AP, FILE
Bunting hangs on the Greenville precinct building in Jersey City, N.J. on Dec. 11, 2019, the day after Detective Joseph Seals was killed by two suspects in an anti-Semitic attack.
(MORE: Note in pocket of gunman in Jewish deli massacre leads to pawnshop owner's arsenal, arrest)

Anderson and Graham were also prime suspects in the slaying of an Uber driver whose body was found on Dec. 7 in Bayonne, New Jersey, near Jersey City, investigators said.

Seals, a member of the Jersey City Police Department since 2006, was promoted to detective in 2017 and worked to take guns of the streets, reported ABC New York Station WABC.

Jersey City POBA
Detective Joe Seals in a photo posted by the Jersey City Police Officers Benevolent Association.

"We believe he was killed while trying to interdict these bad guys," Jersey City Police Chief Michael Kelly said, according to WABC.

(MORE: Van with possible connection to Jersey City Jewish deli shooting found)

Seals was also a "family man," neighbor Joe Vuocolo told WABC. "He loved his children, did everything with them."

NorthJersey.com via USA Today Network
People hold candles at a vigil for Jersey City Detective Joseph Seals outside Queen of Peace Church in North Arlington, N.J., Dec. 15, 2019.
Bryan Anselm/The New York Times/Redux
Mourners line up to enter McLaughlin Funeral Home in Jersey City, N.J., for the wake for Detective Joseph Seals, Dec. 16, 2019.
Bryan Anselm/The New York Times/Redux
Mourners embrace during the wake for Detective Joseph Seals at McLaughlin Funeral Home in Jersey City, N.J., Dec. 16, 2019.

FBI Special Agent in Charge Gregory Ehrie on Monday asked anyone with information about the suspects to call 1-800-CALL-FBI.

"The community needs to know that we continue to follow all leads in this investigation and will leave no stone unturned to find the facts connected with this case," Ehrie said.

Shannon Stapleton/Reuters
Police officers carry flags ahead of the funeral service for Jersey City Police Detective Joseph Seals at St. Aedan's Church in Jersey City, N.J., Dec. 17, 2019.

ABC News' Aaron Katersky and Bill Hutchinson contributed to this report.