The release of the search warrant shed light on why it happened, and then weeks later, the courts unsealed an even more sensitive document.

 Federal charges under the Espionage Act used to justify Trump search are rare.

Investigators questioning Trump aides about handling records could build a case, experts say

Prosecutors weigh evidence to bring charges against potential for revealing secrets.

Criminal statutes cited by the Justice Department in the search of Donald Trump’s Florida estate for mishandled documents are rarely prosecuted, but legal experts say investigators may still be building a criminal case rather than simply retrieving classified records.

In short, because the US Department of Justice suspects the former president may have committed a crime.

We already knew from the search warrant that FBI agents gathered evidence on 8 August as part of an investigation into whether Mr Trump improperly handled government records by taking them from the White House to Mar-a-Lago.

It's worth noting here that US presidents must transfer all of their documents and emails to a government agency called the National Archives.

And earlier this year, that agency said it had retrieved 15 boxes of papers from Mar-a-Lago which Mr Trump should have handed over when he left the White House.