The FBI raided Donald J. Trump’s Mar-a-Lago home today, according to the former President. They did so on the anniversary of another criminal Republican president announcing his resignation: Richard Nixon.

The very fact that the FBI got a search warrant for Mar-a-Lago means that a federal judge found probable cause that a crime was committed and further evidence would be found at Trump’s home in Florida.

This is a really big deal. Not only because raiding a former president’s home is a big deal under any circumstances and certainly in highly politicized environments like the one in which we currently live, but also because given all of those concerns, whatever evidence the DOJ has must be incredibly compelling (and therefore, concerning) to many, not just a few. The search warrant request would be signed off by top DOJ and an independent judge had to agree a “raid” (this is Trump’s word) was warranted.

The FBI appears to have been looking for material that Trump took with him when he left the White House. The AP has a source that relayed that the FBI search was related to “whether Trump took classified information from the White House.” This suggestion was also fleshed out by the New York Times :

The search, according to multiple people familiar with the investigation, appeared to be focused on material that Mr. Trump had brought with him to Mar-a-Lago, his private club and residence, when he left the White House. Those boxes contained many pages of classified documents, according to a person familiar with their contents.

Mr. Trump delayed returning 15 boxes of material requested by officials with the National Archives for many months, only doing so when there became a threat of action being taken to retrieve them.

Multiple legal experts agree that the DOJ almost never prosecutes mishandling of classified materials “unless that material is transferred to a third party.”

Trump wailed about “prosecutorial misconduct” but Representative Ted Lieu pointed out “This is not prosecutorial misconduct because prosecutors don’t approve warrants. This search occurred because a federal judge found probable cause that evidence of a crime would be at Mar-a-Lago.”

“Proceeding by search warrant and not by subpoena is done when you don’t think the recipient of the subpoena will comply with it. In the case of DJT that is a safe assumption,” Andrew Weissmann noted. Weissmann spent 20 years at the DOJ, and when it comes to interpreting their moves is an expert.

The DOJ kept this tightly wrapped with no leaks, as CBS News’Ed O’Keefe shared that a senior White House official told him the West Wing was given no advanced heads up of the raid.

Watergate and FBI historian Garrett Graff shared a thread in which he noted that “The idea the FBI launched a raid on a former president would have been approved and monitored at the highest level of the Justice Department; hard to even imagine how high the bar of probable cause must’ve been for the Bureau to initiate such a politically sensitive search….”

And ultimately, given the seriousness of a search like this, the secrecy with which it was conducted, and the bar that had to be reached in order to obtain not only top DOJ okays but an independent federal judge as well, “Taken together, this is one of the most significant, sensitive, and politically explosive actions the US Justice Department and FBI has ever taken—one of a tiny handful of times it’s ever investigated a president. Bottom line: The FBI & DOJ must’ve known they had the goods.”

Now we have to wait to find out what those goods are, and if they do involve Trump giving, sharing or selling classified information – and if so, to whom.