NEW YORK >> Mounds of paper piled on his desk. Framed magazine covers and keepsakes lining the walls. One of Shaquille O’Neal’s giant sneakers displayed alongside football helmets, boxing belts and other sports memorabilia, crowding his Trump Tower office and limiting table space.

Well before he entered politics, former President Donald Trump had a penchant for collecting. And that lifelong habit — combined with his flip disregard for the rules of government record keeping, his careless handling of classified information, and a chaotic transition born from his refusal to accept defeat in 2020 — have all culminated in a federal investigation that poses extraordinary legal and political challenges.

The search of Trump’s Mar-a-Lago club earlier this month to retrieve documents from his White House years was an unprecedented law enforcement action against a former president who is widely expected to run for office once again. Officials have not revealed exactly what was contained in the boxes, but the FBI has said it recovered 11 sets of classified records, including some marked “sensitive compartmented information,” a special category meant to protect secrets that could cause “exceptionally grave” damage to U.S. interests if revealed publicly.

Why Trump refused to turn over the seized documents despite repeated requests remains unclear. But Trump’s flouting of the Presidential Records Act, which outlines how materials should be preserved, was well documented throughout his time in office.

He routinely tore up official papers that later had to be taped back together. Official items that would traditionally be turned over to the National Archives became intermingled with his personal belongings in the White House residence. Classified information was tweeted, shared with reporters and adversaries — even found in a White House complex bathroom.

John Bolton, who served as Trump’s third national security adviser, said that, before he arrived, he’d heard “there was a concern in the air about how he handled information. And as my time went on, I could certainly see why.”

Others in the Trump administration took more care with sensitive documents. Asked directly if he kept any classified information upon leaving office, former Vice President Mike Pence told The Associated Press on Friday, “No, not to my knowledge.”

The investigation into Trump’s handling of documents comes as he’s facing mounting legal scrutiny on multiple fronts. A Georgia investigation into election interference has moved closer to the former president, with former New York City Mayor Rudy Giuliani, a top defender, informed earlier this month that he is a target of a criminal probe.

Meanwhile, Trump invoked his Fifth Amendment protection against self-incrimination as he testified under oath in the New York attorney general’s long-running civil investigation into his business dealings. A top executive at the business pleaded guilty last week in a tax fraud case brought by the Manhattan district attorney.

But few legal threats have galvanized Trump and his most loyal supporters like the Mar-a-Lago search. The former president and his allies have argued the move amounts to political persecution, noting the judge who approved the warrant has given money to Democrats. The judge, however, has also supported Republicans. And White House officials have repeatedly said they had no prior knowledge of plans to search the estate.

Trump allies have tried to claim the presidency granted him unlimited power to unilaterally declassify documents without formal declaration. But David Laufman, the former chief of the Justice Department’s counterintelligence section, said that’s not how it works.

“It just strikes me as a post hoc public affairs strategy that has no relationship to how classified information is in fact declassified,” said Laufman, who oversaw the investigation into Hillary Clinton’s personal email server during her tenure as secretary of state. While he said it is true that there is no statute or order that outlines procedures the president must abide by to declassify information, “at the same time it’s ludicrous to posit that a decision to declassify documents would not have been contemporaneously memorialized in writing.”

It’s “not self executing,” he added. “There has to be some objective, contemporaneous, evidence-based corroboration of the claims that they’re making. And of course there won’t be because they’re making it all up.”

The decision to keep classified documents at Mar-a-Lago — a property frequented by paying members, their guests and anyone attending the weddings, political fundraisers, charity dinners and other events held on site — was part of a long pattern of disregard for national security secrets. Former aides described a “cavalier” attitude toward classified information that played out in public view.

There was the dinner with then-Japanese Prime Minister Shinzo Abe on Mar-a-Lago’s patio, where fellow diners watched and snapped cellphone photos as the two men reviewed details of a North Korean missile test.

There was the time Trump revealed highly classified information allegedly from Israeli sources about Islamic State militants to Russian officials. And there was the time he tweeted a high-resolution satellite image of an apparent explosion at an Iranian space center, which intelligence officials had warned was highly sensitive. Trump insisted he had “the absolute right” to share it.

Former White House press secretary Stephanie Grisham said Trump was “careless” with sensitive and classified information and “seemed never to bother with why that was bad.”

Grisham recalled one incident involving Conan, a U.S. military dog hailed as a hero for his role in the raid that killed Islamic State leader Abu Bakr al-Baghdadi. She said that before the dog’s arrival at the White House, staff had received a briefing in which they were told the dog could not be photographed because the images could put his handlers in danger. But when the dog arrived, Trump decided he wanted to show it off to the press.

“Because he wanted the publicity, out went Conan,” she said. “It’s an example of him not caring if he put lives in danger. … It was like its his own shiny toy he’s showing off to his friends to impress them.”

Bolton said that, during his time working for Trump, he and others often tried to explain the stakes and the risks of exposing sources and methods.

“I don’t think any of it sank in. He didn’t seem to appreciate just how sensitive it was, how dangerous it was for some of our people and the risks that they could be exposed to,” he said. “What looks like an innocuous picture to a private citizen can be a gold mine to a foreign intelligence” entity.

“I would say over and over again, ‘This is really sensitive, really sensitive.’ And he’d say, ‘I know’ and then go and do it anyway.”

Bolton said that top intelligence officials would gather before briefings to discuss how best to handle sensitive subjects, strategizing about how much needed to be shared. Briefers quickly learned that Trump often tried to hang onto sensitive documents, and would take steps to make sure documents didn’t go missing, including using iPads to show them to him.

“Sometimes he would ask to keep it and they’d say, ‘It’s really sensitive.’ Sometime he just wouldn’t give it back.”

Trump’s refusal to accept his election loss also contributed to the chaos that engulfed his final days in office. The General Services Administration was slow to acknowledge President Joe Biden’s win, delaying the transition process and leaving little time to pack.

While other White House staff and even the former first lady started making arrangements, Trump largely refused. At the same time, White House staff were departing in droves as part of the regular “offboarding process,” while morale among others had cratered in the aftermath of the Jan. 6 attack on the U.S. Capitol.

Bolton said he doubted that Trump had taken documents for nefarious reasons, and instead thought Trump likely considered them “souvenirs” like the many he’d collected through his life.

“I think he just thought some things were cool and he wanted them,” Bolton said. “Some days he liked to collect french fries. Some days he liked to collect documents. He just collected things.”

The Washington Post first reported in February that the National Archives had retrieved 15 boxes of documents and other items from Mar-a-Lago that should have been turned over to the agency when Trump left the White House. An initial review of that material concluded that Trump had brought presidential records and several other documents that were marked classified to Mar-a-Lago.

The investigation into the handling of classified material intensified in the spring as prosecutors and federal agents interviewed several people who worked in the Trump White House about how records — and particularly classified documents — were handled during the chaotic end of the Trump presidency, a person familiar with the matter told The Associated Press. Around the same time, prosecutors also issued a subpoena for records Trump was keeping at Mar-a-Lago and subpoenaed for surveillance video from Mar-a-Lago showing the area where the records were being stored, the person said.

A top Justice Department official traveled to Mar-a-Lago in early June and looked through some of the material that was stored in boxes. After that meeting, prosecutors interviewed another witness who told them that there were likely additional classified documents still stored at Mar-a-Lago, the person said. The person was not authorized to discuss the matter publicly and spoke on condition of anonymity.

The Justice Department later sought a search warrant and retrieved the additional tranches of classified records.