Maurene Comey told colleagues in a farewell email that she was fired as a federal prosecutor without being told a reason but urged them not to succumb to the "fear" she said her termination could cause.

       “If a career prosecutor can be fired without reason, fear may seep into the decision of those who remain,” Comey said in her email, a copy of which was obtained by ABC News. “Do not let that happen.”

       Comey, daughter of former FBI director James Comey, was fired Wednesday after President Donald Trump vented to subordinates about having a Comey working in his administration, sources told ABC News.

       "Yesterday was unexpectedly my last day in the Office. I was summarily fired via memo from Main Justice that did not give a reason for my termination," Comey wrote in the email.

       MORE: Maurene Comey, federal prosecutor in Sean 'Diddy' Combs and Ghislaine Maxwell cases, fired: Sources

       Comey was a highly regarded assistant U.S. attorney for the Southern District of New York, where she worked on cases against Jeffrey Epstein and his convicted associate Ghislaine Maxwell.

       "Every person lucky enough to work in this office constantly hears four words to describe our ethos: Without Fear or Favor. Do the right thing, the right way, for the right reasons without fear of retribution and without favor to the powerful," she wrote in the email.

       "For the majority of my nearly ten years in SDNY, fear was never really conceivable. We don't fear bad press; we have the luxury of exceptional security keeping us physically safe; and, so long as we did our work with integrity, we would get to keep serving the public in this office. Our focus was really on acting 'without favor.' That is, making sure people with access, money, and power were not treated differently than anyone else; and making sure this office remained separate from politics and focused only on the facts and the law," the email read.

       Comey urged her colleagues to continue to fight abuses of power, seek justice for victims and dedicate themselves to “truth above all else.”

       “Fear is the tool of a tyrant, wielded to suppress independent thought,” Comey’s email said.

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       White House press secretary Karoline Leavitt didn't answer questions on the firing of Comey at the press briefing on Thursday.

       Leavitt referred reporters to the Justice Department, saying that it was their decision to fire her.

       The press secretary was later asked whether the White House had knowledge of the firing and whether Trump signed off on it. She again sidestepped, saying only that it was a decision from the DOJ.

       ABC News' Michelle Stoddart contributed to this report.