The standoff between President Donald Trump and his former FBI director intensified Tuesday with the news of James Comey’s memo saying that Trump asked him to shut down the agency’s investigation into ousted national security adviser Michael Flynn.

A person who had seen the memo told The Associated Press what Comey had written. The person was not authorized to discuss the memo by name and spoke on condition of anonymity. The existence of the memo was first reported by The New York Times.

The White House denied the account.

The development comes as the Trump administration faces questions over why and how the president fired Comey last week as the FBI was investigating whether Trump’s presidential campaign was connected to Russian meddling in the election.

Trump wrote to Comey that the dismissal was necessary to restore public trust and confidence. Often lauded for his independence, Comey had come under intense scrutiny in past months for his role in the agency’s investigation into the email practices of Trump’s opponent, Democrat Hillary Clinton, including a pair of letters he sent to Congress on the matter in the final days of the campaign.

A look at key moments in Comey’s tenure, the lead-up to Trump’s decision to fire him and developments since then.

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Sept. 4, 2013: Comey is sworn in to office as the seventh director of the FBI. He was nominated for the post by President Barack Obama and confirmed by the Senate.

July 5, 2016: He holds news conference to announce that “no reasonable prosecutor” would bring criminal charges against Hillary Clinton, the Democratic presidential candidate, over her email practices as secretary of state, but criticizes Clinton and her staff for being “extremely careless” in their handling of classified material.

July 5, 2016: Republican presidential candidate Donald Trump calls the FBI’s decision not to bring criminal charges against Clinton the greatest example yet that the system is “rigged.”

July 7, 2016: Comey vigorously defends the decision not to prosecute Clinton over her use of a private email server as secretary of state. Under an onslaught of Republican criticism, Comey says that to charge Clinton would have been unwarranted and mere “celebrity hunting.”

Oct. 28, 2016: Days before the election, Comey informs Congress by letter that he is reopening the investigation into Clinton’s email practices based on new evidence, citing the discovery of emails on a laptop used by a top Clinton aide. Justice Department officials warn Comey against sending the letter, saying that doing so would be inconsistent with department policy meant to avoid the appearance of prosecutorial interference or meddling in elections.

Oct. 28, 2016: Trump reacts to FBI’s decision to investigate new messages related to Clinton’s emails, telling a campaign rally that he has “great respect for the FBI for righting this wrong.”

Nov. 6, 2016: Comey tells Congress in a follow-up letter that a review of newly discovered Clinton emails has “not changed our conclusions” that she should not face criminal charges.

Nov. 6, 2016: Trump criticizes Comey’s second letter to Congress, saying Clinton was being protected by a “rigged system” and pronouncing her “guilty,” despite the FBI’s conclusion that criminal charges were unwarranted.

Nov. 8, 2016: Trump is elected president.

Nov. 12, 2016: During a telephone call with top campaign donors, Clinton blames Comey for her defeat by Trump. Clinton said her campaign was on track to win the election until Comey sent the letter to Congress on Oct. 28.

Nov. 13, 2016: In a CBS “60 Minutes” broadcast after the election, Trump says he hasn’t decided whether to keep Comey.

Jan. 6, 2017: Comey is among a group of four top U.S. intelligence officials who brief the president-elect on their conclusions that Russia meddled in the presidential election on his behalf. Trump tells The Associated Press by telephone after the meeting that he “learned a lot” but declines to say whether he accepted their conclusion about Russia.

Jan. 22, 2017: Two days after taking office, Trump appears to single out Comey at a White House reception to thank law enforcement officers and others that helped during the inauguration. Trump calls Comey over to where he is standing in the Blue Room to offer a handshake and a partial hug, then comments that Comey has “become more famous than me.”

Jan. 27, 2017: At one-on-one dinner at the White House, Trump asks Comey to pledge his loyalty to the president and Comey declines, according to a person close to Comey, speaking after the FBI director was fired. The White House denies that account.

Feb. 14, 2017: Comey speaks with Trump in the Oval Office a day after Flynn is ousted. A memo that Comey wrote after the meeting, which became public May 16, says Trump asked him to shut down the FBI investigation into Flynn and his Russia ties.

March 8, 2017: During a cybersecurity conference at Boston College, Comey says he plans to serve his entire 10-year term, quipping, “You’re stuck with me for another 6? years.”

March 20, 2017: Comey testifies to Congress that the FBI has been investigating possible links between Trump associates and Russian officials since July, the same month he held an unusual news conference to discuss the investigation into Clinton. Comey had previously refused to acknowledge the parallel Trump investigation, and his disclosure enrages Democrats who already blamed Comey for costing Clinton the presidency.

March 20, 2017: Comey testifies at the same hearing that the FBI and Justice Department have no information to back up Trump’s unsubstantiated claim on Twitter that Obama wiretapped him before the election.

May 2, 2017: Clinton again lays part of the blame for losing the election on Comey’s Oct. 28 letter. “If the election were on Oct. 27, I would have been your president,” she tells a women’s luncheon in New York.

May 3, 2017: Testifying before the Senate Judiciary Committee, Comey insists he was consistent in his handling of the separate investigations into Clinton and Trump. Comey also says it made him feel “mildly nauseous” to think his actions in October might have influenced the election outcome. But he tells senators: “I can’t consider for a second whose political futures will be affected and in what way. We have to ask ourselves what is the right thing to do and then do it.”

May 9, 2017: Comey sends Congress a letter correcting his prior sworn testimony regarding emails handled by longtime Clinton associate Huma Abedin. Comey had told Congress that Abedin had sent “hundreds and thousands” of emails to her husband’s laptop, including some with classified information. The two-page, follow-up letter said that, in fact, only “a small number” of the thousands of emails found on the laptop had been forwarded there while most had simply been backed up from electronic devices.

May 9, 2017: Trump abruptly fires Comey. “It is essential that we find new leadership for the FBI that restores public trust and confidence in its vital law enforcement mission,” Trump states in a letter addressed to Comey. In announcing the firing, the White House circulates scathing memo, written by Deputy Attorney General Rod Rosenstein criticizing Comey’s handling of the Clinton probe.

May 11, 2017: Trump, in an NBC interview, says he had been intending to fire Comey — whom he derided as a “showboat” and “grandstander” — for months. He denies it had anything to do with the Russia investigation, but also says: “In fact 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.”

May 12, 2017: Trump tweets that Comey “better hope that there are no ‘tapes’ of our conversations before he starts leaking to the press!”

May 16, 2017: A person familiar with the situation tells The Associated Press that Comey wrote a memo after the Feb. 14 meeting with the president that said Trump had asked him to shut down the FBI investigation into Flynn. The person had seen the memo but was not authorized to discuss it by name and spoke on condition of anonymity. The White House denies the account. Rep. Jason Chaffetz, the Republican chairman of a House oversight panel, vows to get copies of any memos Comey wrote about meetings with Trump, tweeting: “I have my subpoena pen ready.”

(AP)