Very few people are ever on the receiving end of the FBI search warrant—even fewer end up escaping criminal charges.

The fact that a former president of the United States now ranks among the former provides the strongest indication yet that Donald Trump may soon face the latter.

Monday’s search of Trump’s Mar-a-Lago property in Florida was surely one of the most significant, sensitive, and politically explosive actions the US Justice Department and FBI have ever taken. It’s one of a tiny handful of times the DOJ has ever investigated a president. And it’s an action that likely indicates that the FBI and prosecutors had specific knowledge of both a definable crime and the evidence to back it up.

The actual search warrant, which would list specific crimes being investigated, has not been released yet. According to Monday night news reports, however, the search focused on questions about a number of boxes of classified documents that Trump took from the White House to his Florida mansion after leaving the presidency.

While it may take months to learn more about the underlying investigation, the fact that the FBI launched such a high-profile search already tells us a great deal about the state of the Justice Department’s case.

Here are the five big takeaways.

Probable Cause Was Clear

Federal search warrants aren’t fishing expeditions. The FBI’s legally authorized search of a former president’s primary residence would have been approved and monitored at the highest level of both the FBI and the Justice Department, likely including both the deputy attorney general and the attorney general. It’s hard to imagine how high the bar of probable cause must’ve been for the Bureau to initiate such a politically sensitive search. Ironically, the scandals the FBI has weathered from past Trump investigations likely made the bar for probable cause and sign-off by the department’s upper levels even higher.

One of the biggest scandals the FBI and Justice Department have endured in recent years was the sloppy (and ultimately illegal) paperwork surrounding a FISA warrant filed amid the 2016 presidential campaign that targeted Trump aide Carter Page. Ultimately, two of the four warrants used in that case were later declared invalid, and an FBI lawyer pleaded guilty to falsifying part of the underlying evidence and probable cause paperwork. A nearly 500-page inspector general report eviscerated the Bureau’s handling of the FISA warrants, which were long thought to be one of the most thorough and careful of court filings and which are supposed to be backstopped by careful evidence reviews known as the “Woods procedures.” As it turned out, the FBI had omitted key questions about the underlying evidence from the Page warrant application and offered misleading characterizations about other pieces of evidence.

That scandal led to internal FBI and Justice Department reforms that would have made the Mar-a-Lago search warrant subject to even closer scrutiny—and ensured that the bar for probable cause would have been so high, the evidence so crystal clear, that it’s likely that the Justice Department already feels it has enough information to bring criminal charges.

A Judge Signed Off on the Search

A legally authorized search warrant is an important part of the US Constitution’s system of checks and balances. It requires the assent of two of the three branches of government, whereby the executive branch (the DOJ and the FBI) gets the sign-off of the judicial branch. In the case of the Trump property search, once agents and prosecutors assembled their evidence, an independent federal magistrate judge needed to agree that a crime was likely committed and that there was specific evidence at Mar-a-Lago that would have bearing on the crime.

Notably, this is at least the second time this year that a federal judge has agreed that Trump was at least adjacent to a crime. As the January 6 congressional committee has repeatedly pointed out, a federal judge agreed with its assessment this spring that Trump “more likely than not” committed a crime amid his efforts to overturn the 2020 elections.

This Isn’t Just About Trump Taking Classified Docs

One of the most important questions in an investigation is about establishing motive, summed up in the Latin phrase cui bono. Who benefits? Sure, Trump taking home classified documents is technically a crime. But as national security reporter Zach Dorfman points out, it’s hardly a serious enough offense to spur the FBI to raid the home of a former president.

The entire security classification system exists to serve the presidency: The president is the one official in the US government with the ability to unilaterally declassify any piece of information. (Trump famously exercised this power while in office by tweeting a highly classified satellite photo of an Iranian facility). Plus, while classified documents theoretically include highly sensitive information that would damage national security if released, the reality is that many classified documents aren’t that sensitive.