Special counsel Robert Mueller wrapped up his 675-day probe—the most politically charged investigation in American history—with a profoundly unsatisfying conclusion about whether President Donald Trump obstructed justice: Maybe.

The answer came in a convoluted four-page letter to Congress from newly installed attorney general Bill Barr, who spent the weekend sorting through Mueller’s final report with deputy attorney general Rod Rosenstein.

“The Special Counsel’s investigation did not find that the Trump campaign or anyone associated with it conspired or coordinated with Russia in its efforts to influence the 2016 US presidential election,” Barr wrote in his letter to Congress, summarizing the principal conclusions of the first part of Mueller’s report. The second part covers the president’s actions and whether they count as obstruction. On that question, Barr writes, “the Special Counsel states that ‘while this report does not conclude that the President committed a crime, it also does not exonerate him.’”

Mueller’s report appears as tenacious and thorough as was to be expected of the former FBI director and longtime prosecutor: Barr reported that Mueller’s team of 19 lawyers, alongside 40 FBI agents, analysts, forensic accountants, and other staff, issued more than 2,800 subpoenas, executed nearly 500 search warrants, pulled more than 230 sets of communication records, collected details from nearly 50 pen registers used to track telephone calls, and made 13 requests of foreign governments and law enforcement agencies for additional evidence. They also interviewed around 500 witnesses, although Mueller was unable to question in person a few key figures—namely, the president as well as his children Ivanka and Don Jr.

Along the way, Mueller’s team brought charges against nearly three dozen individuals—including Trump’s campaign chair, deputy campaign chair, national security adviser, and personal lawyer. They also made public, in stunning detail, the extent of the Russian government’s attack on the 2016 election, both its active cyber penetrations targeting Democratic campaigns and state-level voting systems, as well as its online information influence operations. He brought nearly 200 criminal charges, sent five people to prison, collected seven guilty pleas, and won a conviction in the probe’s single trial.

Over the course of his investigation, Mueller established two separate criminal conspiracies to aid President Trump’s election in 2016: one by the Russians, the second involving Trump himself, who was named as an unindicted co-conspirator in the campaign-finance felony charges over hush money payments made to cover his affairs with Stormy Daniels and Karen McDougal. (Trump lawyer and fixer Michael Cohen pleaded guilty to his role in that conspiracy, making clear that Donald Trump directed the cover-up.)

But Mueller apparently will never answer one way or the other whether the president’s actions count as obstruction. Instead, according to Barr, his report lays out the evidence on both sides of the question. The full final results of Mueller’s investigation, however long the “comprehensive” document may turn out to be, though, remain under lock and key at the Justice Department. Barr set no timetable for making more of it public, saying that it needs to go through a careful review first.

Barr’s summary of Mueller’s two top-line conclusions—that the president didn’t collude with Russia and may or may not have obstructed justice—were enough to give Republicans cause for celebration and Democrats heartburn. President Trump promptly tweeted, “No Collusion, No Obstruction, Complete and Total EXONERATION. KEEP AMERICA GREAT!”

In his letter, Barr said he and Rosenstein concluded that the evidence is “not sufficient” to support charging Donald Trump with obstruction, even leaving aside the thorny question of whether the president himself can be indicted. Barr’s decision, though, is sure to launch questions and subpoenas from congressional Democrats, given that before he took office he wrote an unsolicited memo arguing that Mueller was wrongly investigating Trump for obstruction.