President Donald Trump's decision to fire FBI Director James Comey was the culmination of several weeks of guidance from confidants, a week's worth of fuming, and the coup de grâce — a recommendation from his own Justice Department, Politico and CNN reported, citing unnamed sources.

Trump quickly took to Twitter to deny the report, taking aim at CNN, which he repeatedly has accused of spreading "fake news."

The Roger Stone report on @CNN is false - Fake News. Have not spoken to Roger in a long time - had nothing to do with my decision. — Donald J. Trump (@realDonaldTrump) May 10, 2017

When Trump received a letter from Attorney General Jeff Sessions and Deputy Attorney General Rosenstein calling for Comey's dismissal, Trump moved so fast that he didn't inform Comey himself and most of the White House was caught by surprise, Politico reported.

At the center of Trump's decision is Roger Stone, the president's longtime confidant and adviser, who, according to Politico, had been pressing Trump for weeks to can Comey.

Trump's decision to do just that came a few hours after the FBI sent a letter to the Senate Intelligence Committee, correcting testimony that Comey had made about classified Hillary Clinton emails ending up on the computer of top aide Huma Abedin's estranged husband, Anthony Weiner.

But that misstep apparently didn't play into Trump's decision; the president had been fuming for a week over Comey's Senate testimony and investigation into ties between Russia and Trump's campaign, despite the fact Comey, allegedly, told Trump that he was not under investigation.

Politico reports some thinking that the letter from Sessions and Rosenstein simply provided Trump with a rationale to fire Comey.

"We just have no idea why this happened," one recently retired FBI official told Politico. "Everyone is just shocked that this happened."

Roger Stone's new book "The Making of the President 2016: How Donald Trump Orchestrated a Revolution."