(CNN) FBI Director James Comey was fired abruptly Tuesday by President Donald Trump, and the White House has scrambled since then to explain how Trump reached his decision.

Here's a look at what led to Comey's firing and what's happened in the aftermath:

May 2

Hillary Clinton says she was on her way to winning the presidency until the FBI director wrote a letter to Congress saying he was reopening the investigation into her use of a private email server 11 days before the November 8 election.

Trump tweets a response that night: "FBI Director Comey was the best thing that ever happened to Hillary Clinton in that he gave her a free pass for many bad deeds!"

FBI Director Comey was the best thing that ever happened to Hillary Clinton in that he gave her a free pass for many bad deeds! The phony... — Donald J. Trump (@realDonaldTrump) May 3, 2017

...Trump/Russia story was an excuse used by the Democrats as justification for losing the election. Perhaps Trump just ran a great campaign? — Donald J. Trump (@realDonaldTrump) May 3, 2017

May 3

JUST WATCHED Comey: 'Nauseous' over election thoughts Replay More Videos ... MUST WATCH Comey: 'Nauseous' over election thoughts 00:29

Comey, testifying before senators in a committee hearing, says he's "mildly nauseous" at the idea he influenced the election when he reopened the Clinton email investigation. Still, he defended his decision to do so.

At the time, Trump said that Comey's decision "took guts" and that the FBI chief "brought back his reputation" by reopening the investigation.

In his testimony, Comey says he publicly announced his conclusions in the Clinton email investigation after deciding the Justice Department's credibility had been affected by then-Attorney General Loretta Lynch's airport tarmac meeting with former President Bill Clinton.

Comey adds the Russians are still meddling in US politics because they may have concluded, "This works."

At the daily press briefing, White House press secretary Sean Spicer says Trump "has confidence" in Comey.

Sometime last week

JUST WATCHED Durbin believes Comey requested more resources Replay More Videos ... MUST WATCH Durbin believes Comey requested more resources 01:23

Comey asks the Justice Department for more resources for the investigation into Russian meddling in the US election, according to two sources familiar with the discussion . A Justice Department spokeswoman denies Comey did so.

May 8

JUST WATCHED Trump tweets: Russia-Trump collusion a hoax Replay More Videos ... MUST WATCH Trump tweets: Russia-Trump collusion a hoax 01:11

Trump tweets the investigation into Russia's possible collusion with his campaign is a "total hoax" and a "taxpayer funded charade."

The Russia-Trump collusion story is a total hoax, when will this taxpayer funded charade end? — Donald J. Trump (@realDonaldTrump) May 8, 2017

May 9

JUST WATCHED Trump fires FBI Director James Comey Replay More Videos ... MUST WATCH Trump fires FBI Director James Comey 00:58

Trump fires Comey , effective immediately. In his dismissal letter , Trump cites a recommendation from Deputy Attorney General Rod Rosenstein, who wrote in an attached memo that Comey's handling of the investigation into Clinton's email server was to blame.

That evening, Spicer, sandwiched between reporters and a large shrub in the White House driveway, says Trump arrived at his decision after receiving the memo from Rosenstein that day.

CNN reports that federal prosecutors have issued grand jury subpoenas to associates of former national security adviser Michael Flynn as part of the investigation into Russian meddling in the election. CNN learned of the subpoenas hours before Comey's firing.

May 10

JUST WATCHED White House furious after photos released with Russians Replay More Videos ... MUST WATCH White House furious after photos released with Russians 01:41

In a morning "tweetstorm," Trump says Democrats have wanted Comey gone for a while and are now faking outrage at his firing.

"Comey lost the confidence of almost everyone in Washington, Republican and Democrat alike. When things calm down, they will be thanking me!"

Comey lost the confidence of almost everyone in Washington, Republican and Democrat alike. When things calm down, they will be thanking me! — Donald J. Trump (@realDonaldTrump) May 10, 2017

In a photo-op with former Secretary of State Henry Kissinger, Trump says he fired Comey "because he wasn't doing a good job."

The same day, Trump meets with Russian Foreign Minister Sergey Lavrov in the Oval Office, but the White House blocks US media from photographing the event. Russian state-sponsored media post photos of the meeting, angering a White House official

Deputy press secretary Sarah Huckabee Sanders says Comey committed "basic atrocities" by going around the Justice Department chain of command and speaking out during the Clinton email investigation. She also says Trump had considered letting Comey go as early as Election Day.

Sanders adds that Trump "and the rest of the FBI" had lost confidence in Comey.

May 11

JUST WATCHED McCabe: Comey has broad support within FBI Replay More Videos ... MUST WATCH McCabe: Comey has broad support within FBI 01:36

Acting FBI Director Andrew McCabe tells members of the Senate intelligence committee that Comey had "broad support" among the FBI's rank and file, contradicting the White House.

"The majority, the vast majority of FBI employees enjoyed a deep, positive connection to Director Comey," he says.

Trump, in an interview with NBC News, says he had already decided to fire Comey before receiving Rosenstein's recommendation.

"Regardless of the recommendation I was going to fire Comey," Trump tells NBC.

Trump also says he was thinking of "this Russia thing " when he made the decision.

"When I decided to just do it, I said to myself, I said 'you know, this Russia thing with Trump and Russia is a made up story, it's an excuse by the Democrats for having lost an election that they should have won'."

May 16

Comey wrote in a memo that Trump asked him to end the investigation into national security adviser Michael Flynn, according to sources familiar with the matter.

Comey was so appalled by the request that he wanted to document it, sources said. Comey shared the memo with senior FBI officials, according to sources.

"I hope you can let this go," the President said, Comey wrote. CNN has not viewed the memo but sources described it to CNN.

The memo is the clearest sign yet of potential interference by Trump with the investigation into whether members of his campaign team colluded with Russian officials.

"Three words: obstruction of justice," said CNN senior legal analyst Jeffrey Toobin. "Telling the FBI director to close down an investigation of your senior campaign adviser for his activities during your campaign for president, if that's true, that is obstruction of justice."