Comey's draft resignation letter, published by the Washington Post, described the impasse as an "apocalyptic situation" where "the Justice Department and I have been asked to be part of something that is fundamentally wrong."
Mueller, who had also threatened to resign, and Comey met separately with Bush the next day, who agreed to "do the right thing, and put the program on a footing that we could certify its legality," Comey testified, avoiding the mass resignation.
After leaving the Justice Department, Comey was general counsel at Lockheed Martin for five years before becoming general counsel at finance firm Bridgewater Associates. Politico reported in 2009 that Obama considered Comey to replace retiring Supreme Court Justice David Souter.
If approved by the Senate as FBI director, Comey will replace Mueller, a friend who has served in the role since 2001. In addition to jointly threatening to resign in 2004, Comey called Mueller from Ashcroft's hospital room to verify that he could not be physically removed.
Mueller gave the commencement address at Comey's alma mater earlier this month.