Out of every detail listed in the 383-page special counsel report, it was the suggestion that President Biden had trouble remembering when his elder son, Beau, died that seemed to anger the president the most.

During a news conference just hours after the report was released, Mr. Biden appeared to struggle to keep his composure when recalling a line, on page 212 of the report, that suggested that “he did not remember, even within several years,” when his son died.

“I know there’s some attention paid to some language in the report about my recollection of events,” Mr. Biden said, his chin quivering either from anger or sadness. “There’s even a reference that I don’t remember when my son died. How in the hell dare he raise that?”

He said he had worn his son’s rosary “since the day he died.”

Beau Biden, who died of brain cancer in 2015, appears 16 times in the pages of the report prepared by Robert K. Hur, the special counsel appointed to investigate Mr. Biden’s handling of classified documents.

Investigators describe combing through boxes filled with mementos sent to the Bidens after Beau’s death. Mr. Biden had kept photos of his son on the campaign trail in a folder marked “Beau Iowa,” and had kept 28 boxes that “contained letters expressing condolences related to the death of Beau Biden,” according to the report.

Mr. Biden had also kept a folder with clippings labeled “Notable Stories on the Life of Beau Biden,” and an envelope labeled “Layout of Beau’s House,” which was described by an assistant to Mr. Biden as particularly important to him.

Investigators also focused on the notebooks Mr. Biden kept as vice president and found that some contained diarylike entries on “purely personal subjects, such as the illness and death of his son.”

In one case, Mr. Biden’s ruminations were just one page away from notes he took during a sensitive meeting held in the White House Situation Room in 2015. Investigators described Mr. Biden as toggling back and forth between emotional and professional topics in conversations with a ghostwriter, Mark Zwonitzer, as he worked on a memoir.

Mr. Biden has blended that gutting personal loss with his political career ever since.

He still sometimes mentions his son in the present tense in private discussions, according to people who have spoken with him. Last weekend, Mr. Biden and Jill Biden, the first lady, visited Beau’s grave in Delaware before the president visited the Biden campaign headquarters.

On Thursday, Mr. Biden sparred with reporters who questioned his memory, even as he made the sort of mistakes in recollection that he and his advisers were hoping to avoid.

Still, a president who has infused his son’s memory into his presidency wanted to make one thing clear, to both the special counsel’s office and to his critics.

“I don’t need anyone to remind me when he passed away,” Mr. Biden said.