WASHINGTON — He appeared a bit thinner, more stooped at the shoulders. When he spoke, there was a perceptible rasp.

Perhaps it was age, or the two years he has spent away from the television cameras, allowing the results of an extraordinary investigation into Russian election interference and efforts to obstruct it by a sitting president to speak for themselves. But Robert Mueller’s surprise appearance at the Justice Department Wednesday — apart from the public spectacle of it — was vintage Mueller.

Like he did for 12 years as FBI director, Mueller offered only the facts. Yet when he was finished talking 10 minutes after walking alone to the stage of a briefing room at the Justice Department's headquarters, his first public words seemed to land with more weight than the text of his 448-page report released last month.

While Mueller did not stray from the report’s principle findings on Wednesday, he appeared to refocus wandering public attention on some of its most sobering conclusions. His remarks rekindled calls for Trump's impeachment among Democrats in the House and those vying to replace him in 2020.

It has been two months since Mueller completed his investigation, and Washington's response since then has been scattershot. Democrats in Congress have launched wide-ranging investigations and some have called for Trump's impeachment. The Justice Department, meanwhile, has chosen to delve into an unusual examination of the origins of the special counsel’s inquiry, specifically whether the government abused its surveillance authority when monitoring Trump campaign associates. And Trump, claiming vindication, has accused some of those who investigated him of treason.

With that political fog as a backdrop, Mueller offered a pointed defense of the special counsel's chief findings, from the the "concerted attack on our political system" waged by the Russian military to his office's deep dive into whether Trump sought to derail the investigation into possible coordination between his campaign and Russia.

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"The matters we investigated were of paramount importance," Mueller said, closely adhering to a nearly four-page written statement. "It was critical for us to obtain full and accurate information from every person we questioned. When a subject of an investigation obstructs that investigation or lies to investigators, it strikes at the core of the government's effort to find the truth and hold wrongdoers accountable."

What is more, Mueller seemed intent Wednesday on offering the fullest accounting yet of perhaps the most controversial aspect of the special counsel's report: the decision not to bring charges against the president while also not clearing him of criminal conduct.

"If we had confidence that the president clearly did not commit a crime, we would have said that," Mueller said, adding that investigators were essentially blocked by long-standing Justice Department policy that prohibits the criminal prosecution of sitting presidents.

"A president cannot be charged with a federal crime while he is in office. That is unconstitutional. Even if the charge is kept under seal and hidden from public view–that too is prohibited...Charging the president with a crime was therefore not an option we could consider."

WASHINGTON, DC - MAY 29: Special Counsel Robert Mueller walks away from the podium after making a statement about the Russia investigation on May 29, 2019 at the Justice Department in Washington, DC. Mueller said that he is stepping down as special counsel and that the report he gave to the attorney general is his last words on the subject.

Then, Mueller, speaking to reporters and an array of television cameras, reminded Congress of its own power, referring to a conclusion contained on page 171 of the April report examining possible obstruction.

"The Constitution requires a process other than the criminal justice system to formally accuse a sitting president of wrongdoing," Mueller said, in a reference to impeachment. "It would be unfair to potentially accuse somebody of a crime when there can be no court resolution of an actual charge."

While Trump viewed Mueller's statement Wednesday much like the April report, as "case closed," Democrats immediately pounced, reviving discussions of possible impeachment proceedings.

"Given that special counsel Mueller was unable to pursue criminal charges against the president, it falls to Congress to respond to the crimes, lies and other wrongdoing of President Trump – and we will do so," said House Judiciary Committee Chairman Jerry Nadler, D-N.Y. "No one, not even the president of the United States, is above the law."

Before Mueller's statement Wednesday, Nadler had been negotiating for the special counsel's public testimony in an effort to advance continuing congressional investigations ranging from Trump's conduct while in office to his outside business dealings.

Yet Mueller, who developed a reputation as FBI director for seldom seeking the spotlight and never relishing it, all but acknowledged a growing discomfort with being thrust into a widening political storm Wednesday, suggesting that his first public words on the remarkable investigation he supervised should also be his last. He said there is little more he can offer lawmakers who have been eager to have him testify in public.

"I hope and expect this to be the only time that I will speak about this matter," he said. "I am making that decision myself; no one has told me whether I can or should testify or speak further about this matter.

"There has been discussion about an appearance before Congress," he went on. "Any testimony from this office would not go beyond our report...the work speaks for itself."

It was a 'drop-the-microphone-moment' for a public official who is accustomed to plowing his own course, whether it be as a career prosecutor who left a white-shoe law firm to pursue murderers, or later as an FBI director who successfully beat back efforts to dismantle the institution in the wake of the terror attacks of Sept. 11, 2001.

With his investigation now "complete," Mueller, 74, said Wednesday that the plan was to return to "private life."

In a politically divided Washington, however, where lawmakers readily wield subpoena power, private life may be just an aspiration for the man whose surname has for two years been the adjective in its central political drama.

Immediately after thanking Mueller for his his "lifetime of public service“ as a Marine combat veteran, longtime prosecutor and FBI director, House Intelligence Committee Chairman Adam Schiff, D-Calif., said the special counsel's work was not quite done.

"We look forward to Mueller’s testimony before Congress," Schiff said. "While I understand his reluctance to answer hypotheticals or deviate from the carefully worded conclusions he drew on his charging decisions, there are, nevertheless, a great many questions he can answer that go beyond the report..."

This article originally appeared on USA TODAY: Mueller's first remarks stuck to the facts, refocused attention on Russia, rekindled impeachment talk