Slain NYPD detective who probed Mafia to get ‘well overdue’ headstone — 100 years after his death

He is forgotten no more.

An NYPD detective who was killed during a cigar store hold-up a century ago will finally receive the recognition he deserves Monday – when a headstone inscribed with his name and acknowledging his service is placed on the unmarked grave where he was buried.

The honor is thanks to a retired NYPD lieutenant who learned of the travesty while researching a loved one’s family tree.

Bill Markowski was studying his fiancee’s family history on an online ancestry research site when he discovered that her great-great uncle, Bernardino Grottano, better known as Barney, was buried in famed Green-Wood Cemetery in Brooklyn.

“He was like ‘Oh my God! This is your great uncle!'” recalled fiancee Phyllis Kropacek. “He loves to do the ancestry and then he just followed this up.”

Markowski didn’t know anything else about the man, but said he quickly became intrigued when he “found out he was a police officer and he was killed in the line of duty.”

“So I started looking more and more into it,” he said.

He learned that Grottano was off-duty in downtown Brooklyn the night of May 19, 1924, when a robber ran past him with uniformed cop in pursuit after ripping off a shop at Flatbush Avenue and Fulton Street with an accomplice.

Grottano joined the patrolman in the chase and the suspect opened fire on the officers, prompting them to return fire. Grottano was struck in the chest and fell to the ground.

The patrolman was struck in the arm but survived.

“The 26-year-old perpetrator was also felled during the volley and died at the scene,” according to the Detectives Endowment Association website. “He had a long rap sheet that included grand larceny and drugs.”

Grottano died a week later at Brooklyn Hospital.

Grottano, who lived in Bensonhurst, left behind a wife and two children.

He was once attached to what was then called the Italian Squad in Manhattan, investigating the Mafia.

“As a little girl, my grandfather, every time I went to his house, he constantly talked about Bernardino and he explained exactly what happened,” said Kropacek, who has a 9-year-old grandson. “He had two photos of him as a police officer in the house, one in the living room and one in the bedroom.”

Grottano was buried in Lot No. 26518 Section 143 in Green-Wood Cemetery, a private lot with six graves containing the remains of about 30 people.

The family who owned the lot has a headstone there to commemorate the death of their son, a Navy pilot who went missing, but he isn’t buried there.

Grottano had no marker.

Grottano’s widow, Mary, was juggling hospital bills and had two children to raise alone so couldn’t afford a headstone, according to newspaper stories from the time.

Markowski reached out to Detectives Endowment Association and the union offered to help pay for a headstone.

“Detective Grottano was a hero and won’t be forgotten even after 100 years,” DEA President-elect Scott Munro said.

Current Detective Endowment Association President Paul DiGiacomo agreed.

“His life mattered and his heroic work that fateful night he was shot and killed in 1924 mattered,” he said. “Whether it is one year or 100 years later, the DEA will never forget a fallen union member and their family.”

During his research, Markowski discovered another Grottano relative in the department.

NYPD Police Officer Dylan Grottano, 24, heard growing up that one of his ancestors died in the line of duty.

“That’s part of the reason I joined the NYPD,” Grottano, who works in Brooklyn’s 66th Precinct, told The Post. “It makes it more like a legacy and a family tradition.”

Grottano, who is the fallen officer’s great-great nephew, said he’s thankful his long-lost relative is finally being recognized.

“What he did was honorable, pursuing the perp when he wasn’t on duty,” Grottano said. “It’s well overdue.”