Special counsel Robert Mueller found no proof that President Donald Trump criminally colluded with Russia and reached no conclusion about whether Trump obstructed justice, Attorney General William Barr told Congress on Sunday, while also announcing that he found insufficient evidence to pursue the matter further.

The bombshell findings were contained in a letter that Barr sent to lawmakers summarizing Mueller's report and that was made public.

Barr quoted Mueller's report, which he said stated: "(T)he investigation did not establish that members of the Trump campaign conspired or coordinated with the Russian government in its election interference activities."

READ: Barr's letter to Congress

The report makes it clear that Trump was not exonerated in his behavior, but simply found insufficient criminal evidence to prosecute.

On obstruction of justice, Barr wrote that the special counsel declined "to make a traditional prosecutorial judgment," leaving it up to the attorney general to choose whether to bring obstruction charges against the president. Barr declined to do so, he said in the letter to Congress, based on the evidence presented and Department of Justice guidelines around prosecuting a sitting president.

Mueller did not, Barr said, "draw a conclusion — one way or the other — as to whether the examined conduct constituted obstruction."

"Instead, for each of the relevant actions investigated, the (Mueller) report sets out evidence on both sides of the question and leaves unresolved what the Special Counsel views as 'difficult issues' of law and fact concerning whether the President's actions and intent could be viewed as obstruction," Barr wrote. "The Special Counsel states that 'while this report does not conclude that the President committed a crime, it also does not exonerate him.'"

Trump tweeted a short time later "Complete and Total EXONERATION."

No Collusion, No Obstruction, Complete and Total EXONERATION. KEEP AMERICA GREAT! — Donald J. Trump (@realDonaldTrump) March 24, 2019

Providing Mueller's "principal conclusions," as Barr has referred to them, to lawmakers came after the transmission of the special counsel's report to Barr on Friday that concluded an investigation which has resulted in the indictments of 34 people, infuriated the president and threw the administration into turmoil.

It remains unclear whether Mueller's full report will ever be made public.

The long-awaited end of the probe came almost two years after Mueller was appointed by Deputy Attorney General Rod Rosenstein to investigate "any links and/or coordination between the Russian government and individuals associated with the campaign of President Donald Trump" and "any matters that arose or may arise directly from the investigation."

Among those who have been criminally charged are Trump's former national security adviser Michael Flynn; former campaign chairman Paul Manafort; longtime ex-political adviser Roger Stone; former personal lawyer Michael Cohen; and numerous Russian nationals. There have been a number of guilty pleas and convictions — but none of the charges have directly accused Trump or anyone in his orbit of conspiring with Russians to help Trump get elected in 2016.

President Donald Trump departs the White House on Dec. 8, 2018. Al Drago / NYT via Redux file

There will be no more indictments now that the probe is over, NBC News has learned.

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According to Barr's letter on Sunday, the special counsel's office employed 19 lawyers, 40 FBI agents, intelligence analysts, forensic accountants and other professional staff.

In addition, Mueller issued more than 2,800 subpoenas, executed nearly 500 search warrants, obtained more than 230 orders for communication records, issued almost 50 orders authorizing use of pen registers (which detail to whom and when someone made calls and from where), made requests of 13 foreign governments for evidence, and interview approximately 500 witnesses.

Trump refused be interviewed with Mueller — his lawyers said they were concerned about a "perjury trap" — but he did submit written responses to the special counsel's questions in November.

Mueller was appointed special counsel on May 17, 2017 — eight days after Trump fired James Comey as FBI director. Comey had been leading the investigation into Russian meddling and any possible Trump campaign involvement.

The president initially said he'd removed Comey at the urging of Rosenstein and then-Attorney General Jeff Sessions, but he later told NBC "Nightly News" anchor Lester Holt it was his decision, and the president cited his frustration with the Russia probe.

That fueled law enforcement concerns that Trump was trying to obstruct the investigation — fears that were heightened a day after the firing, when he hosted two Russian diplomats in the Oval Office. "I just fired the head of the FBI. He was crazy, a real nut job," Trump told them, according to The New York Times. "I faced great pressure because of Russia. That's taken off."

Those and other actions taken by the president since the probe began led Mueller to investigate whether Trump was trying to obstruct justice in the case, sources have told NBC News.