The departure was the culmination of a toxic relationship that frayed just weeks into Sessions' tenure, when he stepped aside from the Russia investigation because of his campaign advocacy and following the revelation that he had met twice in 2016 with the Russian ambassador to the U.S.
"It seems like every time we get ahead, Trump breaks another rule", Ferdinandt said.
Trump saw the move as a betrayal and frequently and publicly criticised Sessions for making the decision to recuse himself.
At a protest in support of Mueller outside the White House, a crowd of several hundred protesters shouted anti-Trump slogans.
Those concerns are now focused on the future of the Mueller probe, which began as a look into alleged links with Russians seeking to disrupt the election and expanded into an investigation of billionaire Trump's murky finances, including his business ties to Russia.
In an op-ed in August previous year he publicly urged Deputy Attorney General Rod Rosenstein - who oversees the probe - to "limit the scope of his investigation to the four corners of the order appointing him special counsel".
Justice Department officials said that under normal circumstances, the deputy attorney general would likely play an active, hands-on role in overseeing such a high profile probe, and they had no reason to believe that Rosenstein would now be cut out.
Under the Federal Vacancies Reform Act, Whitaker can serve 210 days without Senate confirmation before the president nominates a permanent attorney general. In an interview past year with a conservative talk radio host, Whitaker said there was "no collusion" between Trump's campaign and Russian Federation, a key question being examined by Mueller.
The 90-minute presser was a finger-wagging spectacle, with Trump repeatedly berating reporters and the media, and some observers comparing him to a drunk uncle at a wedding party as he rambled incoherently on sundry issues in a spectacle that many fear diminishes the United States.
He questioned Deputy Attorney General Rod J. Rosenstein's ability to give Mueller such wide latitude and wanted to explore the bounds of what Mueller was examining, though Rosenstein kept Session's office "walled off" from the matter, this person said. The mobilization comes after President Donald Trump fired Attorney General Jeff Sessions Wednesday, replacing him with a man who has previously criticized the probe and offered suggestions on how to slow it down.
The special counsel's team has been investigating Stone's connection to WikiLeaks during the 2016 campaign and whether he had advance knowledge of the group's plans to release hacked material damaging to Democrat Hillary Clinton.
Sessions took the lead in imposing Trump's travel ban targeting a number of mostly Muslim nations, canceling the so-called Dreamer program that let the children of undocumented immigrants remain in the US and forcing the separation of migrant families as part of a border crossing crackdown.
"Donald Trump may think he has the power to hire and fire whomever he pleases, but he can not take such action if it is determined that it is for the purposes of subverting the rule of law and obstructing justice", Nadler said in a statement.
-With assistance from Steven T. Dennis.