The last time retired NYPD cop William McNaughton could remember speaking to his son James, a staff sergeant in the U.S. Army Reserves stationed in Iraq, was in an Aug. 1, 2005, phone call.

The next day, the elder McNaughton saw an Army colonel standing on the front lawn of his Centereach home and instantly understood the news the officer brought wasn’t good.

“You know,” William McNaughton said Tuesday, explaining why he instantly understood that the colonel’s presence something terrible had happened to his son.

James, 27, and a member of the NYPD’s transit bureau, had been killed by a sniper while guarding prisoners at Camp Victory in Baghdad. He was the first NYPD officer killed in action in Iraq.

In a private ceremony Tuesday, NYPD Commissioner James P. O’Neill pinned the younger McNaughton’s police shield — number 8243 and recoated to give it new luster — on the uniform of newly minted officer Matthew Fallon, 26. Fallon, also a military veteran who served in Afghanistan, graduated from the NYPD’s academy on Dec. 28th.

The new cop was among a group of military veterans finishing academy training in December when William McNaughton and his wife Michelle — James’ stepmother — paid a visit and told them to submit a special statement if they wanted to wear the shield worn by the couple’s fallen son.

Michelle McNaughton remembered how Fallon did something that stood out.

“When we were there speaking, Officer Fallon came down the hallway and thanked us for our sacrifice,” she said in a telephone interview. “He was very heartfelt and emotional.”

In the statement he submitted, Fallon, of Nassau County, wrote of his stint in Afghanistan as a mechanic while also serving in the Fallen Hero Detail, a group escorting the remains of fallen U.S. service members to aircraft for the return home.

“I think about the hero’s [sic] that we sent home every day and because of that I am a better man,” Fallon wrote. “Wearing a shield number that has such a rich history behind it would be an absolute honor for me. It would be a connection for me that is difficult to put into words.”

The badge had been worn for a few years by NYPD Officer Wing Har, also of Nassau County, whose recent promotion to detective meant a new shield number.

“I felt very honored and felt privileged and there is such a great tradition behind that shield number,” said Fallon Tuesday, assigned to the 103rd Precinct in Queens.

William McNaughton worked in the canine unit and after the Sept. 11, 2001, terrorist attacks on the World Trade Center, was doing recovery work at Ground Zero. He said Tuesday he was recently diagnosed with cancer related to his work.