Acting attorney general Sally Quillian Yates, a longtime prosecutor from Atlanta, began her tenure as an Obama appointee two years ago by saying that pursuing justice was more important to her than bringing federal cases in court.
"We're not the Department of Prosecutions or even the Department of Public Safety," Yates said in May, 2015, the week after she was confirmed as Deputy Attorney General, the second-highest ranking position in the Justice Department. "We are the Department of Justice."
Yesterday, only days away from stepping down from her 27-year career in the Justice Department, Yates defied President Donald Trump, ordering federal attorneys not to defend the controversial immigration order issued at the weekend.
Within hours, Trump fired her.
Yates, 56, struggled with her decision over the weekend, said an official who spoke on the condition of anonymity given the sensitivity of the situation. By yesterday, though, she had concluded that she could not ask her federal attorneys to defend the order. Yates could not be reached for comment.
She sent a memo to the civil division of the Justice Department and US attorneys across the country saying she was not "convinced" the order was lawful, and that the department "will not present arguments in defence of the Executive Order, unless and until I become convinced that it is appropriate to do so".
Hours later, Yates received a hand-delivered letter from the White House saying the President was removing her from office.
"She did what she believes was the right thing to do and then she gets fired for it," the official said.
"This is not how she would have preferred to end her 27-year career. But she did what she had to do."
Those who know Yates well said that her action was consistent with the independence and commitment to the rule of law they say she has exhibited throughout her career.
"For nearly three decades, Acting Attorney General Sally Yates has served presidents of both parties, defending the Constitution and holding terrorists and other criminals accountable," said former Labour Secretary Tom Perez, who was head of the civil rights division in the Obama Administration. "Acting Attorney General Yates's record is simply beyond reproach," said Perez, who is running to be chair of the Democratic National Committee.
But Trump's senior policy adviser, Stephen Miller, blasted Yates on Fox News after the acting Attorney General was fired.
"It can't be stated strongly enough how reckless, irresponsible and improper the behaviour was of the acting Attorney General, Sally Yates, in refusing to defend the President's order," said Miller, who accused Yates of "refusing to defend the lawful power of the President". He added that he had no doubt about the legality of the order.
For the past two years, Yates has been responsible for the day-to-day running of the 113,000-employee Justice Department. She was also been responsible for overseeing the Justice Department's work on the prior White House's clemency initiative, in which the President granted commutations to thousands of nonviolent drug offenders who met certain criteria set out by the Administration.
She also wrote a new policy two years ago that became known as "the Yates memo", which made the prosecution of individual executives - not just the corporations that employ them - a top priority for federal prosecutors.
Last month, Yates was one of the Justice officials who announced that federal prosecutors indicted six executives at Volkswagen in connection with the company's diesel emissions scandal; the company agreed to pay US$4.3 billion ($5.9b) in criminal and civil penalties.
Former Justice Department spokeswoman Emily Pierce said that Yates was known in the department for voicing her opinions when she thought the Administration was going in the wrong direction. Pierce said Yates was particularly vocal during a debate over government access to encrypted communications during criminal investigations, when some officials wanted to make it harder for law enforcement to access the locked information.
"She advocated very strongly as a one-woman show for law enforcement and made the Obama Administration pause on policies she thought would be harmful," Pierce said.