US special counsel Robert Mueller on Wednesday announced his resignation and the closure of the office that investigated Russian interference in the 2016 presidential election.
Speaking from the Justice Department more than a month after issuing a 448-page report, Mr Mueller declared the investigation over.
“We are formally closing the special counsel’s office and I am resigning from the Department of Justice,” said Mr Mueller, 74.
After two years of unearthing a massive Russian operation to interfere in the American vote, he called the case “of paramount importance” before announcing his return to private life.
The statement was a declaration that concluded his investigative work and avoided testimony in Congress.
“I hope and expect this will be the only time I will speak to you in this manner,” Mr Mueller said, adding that he decided himself against testifying and that the report “speaks for itself”.
At the same time, in carefully crafted words, he appeared to pass the issue to Congress if any further legal action against US President Donald Trump or his team were to be pursued.
“If we had confidence the president clearly did not commit a crime, we would have said so,” Mr Mueller said.
While Mr Trump claimed that the report exonerated him and cleared him of any attempts to obstruct justice, Mr Mueller avoided using such terms.
He said that charging Mr Trump for a crime was “not an option” for his team because the Justice Department legally prohibits such action against a sitting president.
"It would be unfair to potentially accuse somebody of a crime when there can be no court resolution of an actual charge," Mr Mueller said.
Moments after his statement, Democrats in Congress were calling for action.
The chairman of the House judiciary committee, Jerry Nadler, said that while Mr 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".
Democratic strategist David Axelord predicted that Mr Mueller’s words “are only going to intensify the drumbeat for impeachment”.
This month, Republican Congressman Justin Amash joined some Democrats in pushing for impeachment procedures against Mr Trump.
“The ball is in our court, Congress," Mr Amash tweeted on Wednesday.
But Democratic Speaker of the House Nancy Pelosi has remained hesitant of initiating such hearings.
Mr Trump maintained his position on Wednesday, tweeting after the Mueller statement that “nothing changes from the Mueller Report. There was insufficient evidence and therefore, in our country, a person is innocent. The case is closed".
White House press secretary Sarah Sanders also issued a statement reinforcing the president's view that the case is closed.
"The special counsel has completed the investigation, closed his office, and has closed the case," Ms Sanders said.
"After two years, the special counsel is moving on with his life, and everyone else should do the same."