A longtime friend who talked to the President over the weekend described him as "white hot," a mood that set the table for Comey's firing.
Trump did not seek a wide range of viewpoints on Comey, several people familiar with the matter told CNN, unlike his approach on many difficult choices.
Whether sending more troops to Afghanistan or deciding whether to withdraw from the Paris climate accord, the president often embraces opposing positions, but on Comey there was little room for debate inside the West Wing.
White House chief of staff Reince Priebus initially warned of risks associated with abruptly dismissing Comey -- including the fallout for Trump's legislative agenda -- but people familiar with the decision said it was unclear how forcefully Priebus argued his point when it became clear the President was insistent on firing Comey.
"He wasn't doing a good job," Trump said Wednesday in the Oval Office when asked about Comey. "Very simply, he was not doing a good job."
Those sparse words were all the President had to say about why he fired Comey, aside from several messages on Twitter. He did not answer two critical questions about Comey's dismissal: Why and why now?
"The President had lost confidence in Director Comey," White House spokeswoman Sarah Huckabee Sanders said Wednesday. "Frankly he'd been considering letting Director Comey go since the day he was elected."
Several people familiar with the decision say the President grew increasingly frustrated at Comey after his congressional hearing last Wednesday when he testified that he was "mildly nauseous" over the idea that he helped sway the election. Even the health care victory in the House one day later couldn't take his mind off Comey, two people close to Trump said.
"He wouldn't hear it (that he should be encouraged)," the friend said. "It's Russia. Russia. Trump and Russia." The President complained, with expletives, about Comey's "mildly nauseous" answer and said his answer when pressed on leaks convinced the President he was far less concerned about the leaks than Trump thought he should be.
Communications team kept in dark
One reason the administration underestimated the explosive fallout, several people close to the White House said, because few seasoned political hands were closely involved in the decision. The White House communications team was kept almost entirely out of the loop until Tuesday afternoon.
Several people close to the White House, speaking on condition of anonymity to discuss internal deliberations, described it as a stunning and dispiriting turn of events when they were called to defend and explain one of the most controversial decisions of Trump's young presidency "at almost the same time he pulled the trigger."
More than 24 hours later, the White House was still explaining the timeline of the Comey decision.
Senior administration officials initially insisted on Tuesday the President was following the recommendation of Deputy Attorney General Rod Rosenstein by firing Comey. The White House, by Wednesday, said the President had long been leery of Comey, despite repeatedly saying he had full confidence in him, and finally made a decision he had been mulling all year.
Both explanations were undercut by the president's own letter to Comey, which made clear Russia investigation was at the root of his frustration.
"While I greatly appreciate you informing me, on three separate occasions, that I am not under investigation," Trump wrote. "I nevertheless concur with the judgment of the Department of Justice that you are not able to effectively lead the Bureau."
The White House declined to produce evidence of the three separate occasions the president referenced.
Asked whether the president regretted not firing Comey immediately upon taking office, Sanders had a quick answer.
"No," Sanders said. "I think the president wanted to give Director Comey a chance."
Trump has over the course of past couple months several times expressed frustration "they can't all just make this go away."
"He was mad at Sessions when he recused. Really mad," the friend said. "Mad at his lawyer and the staff. Mad at you guys on TV. Mad at the committees. Mad at Comey. "