By Wednesday, leaders from the Senate intelligence and judiciary committees had sent requests to both the Federal Bureau of Investigation and the White House for all records pertaining to Comey's conversations with Trump.
But according to a person close to the White House, Rosenstein was upset about the narrative that emerged from the White House the evening of May 9.
They included media reports that Trump discussed sensitive intelligence on the Islamic State militant group with Russia's foreign minister.
During his tenure he served both Republican and Democratic presidents, and is highly respected by both parties.
In a pair of Twitter posts on Thursday morning, Trump made clear he was unhappy with the latest development to roil his four-month-old administration. He called it the "single greatest witch hunt".
"This is a truth hunt", said Democratic Senator Amy Klobuchar. Trump has long bristled at the notion that Russian Federation played any role in his November election victory.
The tweets fly in the face of the statement issued on Wednesday night which had appeared as an attempt by Trump's staff to tamp down the raging political storm over Russian Federation which has resulted in Trump's worst week in office so far.
The committee is one of several on Capitol Hill investigating possible collusion between Russian Federation and President Donald Trump's 2016 campaign.
The issue spilled over onto Wall Street on Wednesday, where the S&P 500 and the Dow had their biggest one-day declines since September as investor hopes for tax cuts and other pro-business policies faded amid the political tumult.
Only a special prosecutor appointed under a new independent counsel law can thoroughly investigate the many serious allegations swirling around this administration, and then prosecute if necessary. This recent development even led some Republicans to ask for a special prosecutor for the first time, as seen on Wednesday morning, when IL representative Adam Kinzinger told CNN, "It is time we look at the idea of an independent commission or special prosecutor".
Rosenstein, at an unprecedented closed door session, briefed the entire U.S. Senate today. One of the attendees, speaking on condition of anonymity, described Rosenstein as anxious and nervous and said he drank multiple glasses of water "and spilled one".
Sen. Lindsey Graham (R-SC) came out of a Senate-wide briefing Thursday by the USA deputy attorney general with the impression that the federal probe into Russia's interference in the US election has entered criminal territory.
But Rosenstein added: "I wrote it".
"I believe it hurts our country terribly, because it shows we're a divided, mixed-up, not-unified country", Trump said.
The memo focuses on Comey's handling of the Hillary Clinton email investigation, particularly the FBI director's decision to divulge details to the public at various junctures. Trump said in a tweet.
"That was a poor, poor performance", Trump said. John McCain, R-Ariz., said Trump would be making a mistake to start a rhetorical war with the new investigator.
"You're pretty well knocked out of the game", he said about the ongoing high-profile congressional probes, "and that's probably the way it should be".
"As this investigation progresses - as well as those of the House and Senate Committees - it is important to give the process and people involved our support and patience".
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