"Both Democrats and Republicans attacked the FBI Director at various times for various reasons and called for his ouster", Comstock, who formerly worked with Comey at the Justice Department, said in a statement.
But when questioned whether it was "unusual" that Trump would have received such a notification that he was not under investigation, McCabe said: "I'm not aware of that practice". I hope you won't either.
With Comey gone, there were speculations whether a special prosecutor would be hired to investigate the case, however the White House appeared to shut down the notion.
Deputy press secretary Sarah Huckabee Sanders said on "Good Morning America" today that she was "not aware" of Rosenstein's contemplating his resignation.
So did President Trump ask Mr Rosenstein specifically to investigate Mr Comey's conduct?
The White House says Comey's firing was motivated exclusively by concerns over his handling of the high-stakes probe into Hillary Clinton's emails.
After Donald Trump's administration was once again thrust into controversy following the president's sacking of FBI Director James Comey, Spicer has been accused of hiding among some foliage to escape tricky questions from the media.
Sanders insisted on NBC that Comey's dismissal won't change much.
"Ask Sally Yates, under oath, if she knows how classified information got into the newspapers soon after she explained it to W.H. Council", Trump wrote on Twitter Monday. He also said later he would not update the White House on the ongoing Russian Federation investigation.
The White House press corps were later unexpectedly scrambled to a photo call in the oval office, where Trump was meeting with Henry Kissinger. The investigation has shadowed Trump from the outset of his presidency, though he's denied any ties to Russian Federation or knowledge of campaign co-ordination with Moscow.
McCabe was then asked by the committee's top Democrat Mark Warner whether he would commit to inform the committee of any attempts by the administration to interfere with the Russian Federation investigation and its efforts to find out whether there was any cooperation between Trump campaign aides and Moscow.
Democrats said MNr Trump's move echoed the Watergate scandal of the 1970s that eventually prompted the resignation of Richard Nixon as president.
"Let me disappoint everybody up front", he said.
He raised the prospect that White House stonewalling on a special prosecutor could trigger a drastic congressional response.
The letter marked Mr Comey's first known comments on his firing at the hands of Mr Trump, which sent shockwaves across the country over the timing and perceived breach of due process and natural justice.
"It is my opinion and belief that the FBI will continue to pursue this investigation vigorously and completely", McCabe said, adding that he saw no "crisis of confidence within the leadership of the FBI". "When things calm down, they will be thanking me", Trump tweeted.
But White House officials privately expressed surprise at the level of backlash, particularly from leading Republicans.
"The work of the Federal Bureau of Investigation continues despite changes in circumstance", he told the Senate Intelligence Committee hearing on global threats against the country.
Colbert said he is "pretty confident" in his reasoning. "His dismissal, I believe, is a loss for the Bureau and the nation". Jack Eckenrode, a former special agent in charge of the FBI's Philadelphia division, said the administration "will be hard-pressed to find someone who possesses his unique combination of personal qualities as well as his respect for the rule of law".