For the past seven years, Gen. John F. Kelly has gone out of his way to keep the death of his son free from politics.

He did not talk about him when — just four days after his death in southern Afghanistan — Kelly found himself commemorating two other Marines killed in combat, in a moving speech in St. Louis. In fact, according to a Washington Post report, he specifically asked the officer introducing him not to mention his boy, 1st Lt. Robert M. Kelly, who was killed instantly when he stepped on a land mine while on patrol in 2010.

Just last month, Kelly slipped away from the White House to attend a Marine Corps scholarship golf tournament in his son's memory, with little fanfare or attention.

But on Tuesday, Kelly's boss, President Trump, thrust his son into the public and political glare, invoking the younger Kelly as part of a continuing attack on former president Barack Obama.

In an interview with Fox News radio, Trump singled out Kelly, his chief of staff, as he attempted to bolster his false claim a day earlier that Obama never called families of fallen U.S. service members.

"I think I've called every family of someone who's died," the president told the host, Brian Kilmeade. "As far as other representatives, I don't know. You could ask General Kelly, did he get a call from Obama?"

The remark, which was almost immediately derided by Democrats and Obama allies as politicizing a tragedy, was unplanned, said two White House officials, who said they were caught off-guard by Trump's comments. One said Kelly may have mentioned some details surrounding his son's death to the president in private — and the president then repeated them in public, a relatively frequent occurrence with Trump.

The president's casual assertion sent both sides scrambling to recount their own version of events — underscoring again that in Trump's White House, almost nothing is off limits and just about anything can be used to score political points.

Leon Panetta, former defense secretary under Obama and former White House chief of staff under President Bill Clinton, said Trump's comments were below the dignity of the office.

"I just think it demeans the presidency when you use John Kelly and his son, both of whom are patriots, to back up his excuses for whatever happened," Panetta said. "I just think it creates a sense that there is no sacred ground for this president."

A White House official, speaking on the condition of anonymity because he was not authorized to discuss the matter publicly, said Kelly did not receive a call from Obama at the time.

But in May 2011, Obama hosted a breakfast for Gold Star families — those who had lost a family member who was in uniform — and Kelly and his wife attended, according to White House records.

A person familiar with the event said the couple were seated at then-first lady Michelle Obama's table.

A former Obama White House official, meanwhile, flatly rebutted Trump's initial claim that Obama never — he later backpedaled to suggest rarely — called families of military lost during his administration.

"President Obama engaged families of the fallen and wounded warriors throughout his presidency through calls, letters, visits to Section 60 at Arlington, visits to Walter Reed, visits to Dover, and regular meetings with Gold Star families at the White House and across the country," the official said.

Kelly, who became the highest-ranking military official to lose a child in Iraq or Afghanistan, watched both his sons follow him into the Marine Corps. When Robert died, Kelly and his sons had participated in 11 combat tours in Iraq and Afghanistan combined.

But Kelly has been private about his son's death, even though both his and his sons' military service clearly informs his thinking on White House foreign policy and national security decisions, which to him are not merely intellectual exercises, several White House officials said.

Kelly has previously resisted White House efforts to link children's deaths with politics and policy. Earlier this year, when Trump ordered the Department of Homeland Security to establish the VOICE office — Victims of Immigration Crime Engagement — Kelly, then the homeland security secretary, at the rollout of the office tried to push back internally against efforts to highlight "angel" moms and families whose kids were killed by undocumented immigrants, one department official said. The families were featured at the event but did not have a speaking role.

The official said Kelly is very sensitive to his son's death being politicized, and recoils at attempts to politicize parents and families in this manner.

Still, Kelly has spoken publicly about his son before. He participated in the 2011 Washington Post profile, largely, he said, to highlight the lives and challenges of military families.

Even then, however, his reticence emerged. When first approached about the story, he replied in an email: "We are only one of 5,500 American families who have suffered the loss of a child in this war. The death of my boy simply cannot be made to seem any more tragic than the others."

Since joining Trump's West Wing team, Kelly is almost always at the president's side for public appearances. But he was notably absent Tuesday from a Rose Garden news conference with Trump and the Greek prime minister.

The White House offered no explanation of why Kelly was not in attendance.

Anne Gearan, David Nakamura and Philip Rucker contributed to this report.