Reports over the past 24 hours have made it clear that Trump fired Comey because he was frustrated that the Russia investigation wouldn’t just go away:

Washington Post: “Trump was angry that Comey would not support his baseless claim that President Barack Obama had his campaign offices wiretapped. Trump was frustrated when Comey revealed in Senate testimony the breadth of the counterintelligence investigation into Russia’s effort to sway the 2016 U.S. presidential election. And he fumed that Comey was giving too much attention to the Russia probe and not enough to investigating leaks to journalists.”

It is also clear that the FBI’s Russia investigation was ramping up significantly in the days leading up to Comey’s firing:

Wall Street Journal: “Mr. Comey started receiving daily instead of weekly updates on the investigation, beginning at least three weeks ago, according to people with knowledge of the matter and the progress of the Federal Bureau of Investigation probe. Mr. Comey was concerned by information showing possible evidence of collusion, according to these people.”

CNN: “FBI Director James Comey asked the Justice Department for more resources for the agency's investigation into Russian meddling of the US election and ties to Donald Trump's presidential campaign, just the week before the President fired him.”

CNN: Headline: “Senate Russia investigators ask Treasury for Trump team financial information”

The White House has lied through its teeth about the process that led to Comey’s firing:

Washington Post: Headline: “The White House explanations for Comey’s firing are crumbling before our eyes”

Mediaite: Headline: “Jake Tapper on Comey Firing Tick-Tock: ‘How Many Times Can the White House Just Lie?’”

Washington Post: “But the private accounts of more than 30 officials at the White House, the Justice Department, the FBI and on Capitol Hill, as well as Trump confidants and other senior Republicans, paint a conflicting narrative centered on the president’s brewing personal animus toward Comey.”

Deputy Attorney General Rod Rosenstein reportedly threatened to resign when he saw that the White House was making him out to be the main driver behind Comey’s firing:

Washington Post: “Rosenstein threatened to resign after the narrative emerging from the White House on Tuesday evening cast him as a prime mover of the decision to fire Comey and that the president acted only on his recommendation, said the person close to the White House, who spoke on the condition of anonymity because of the sensitivity of the matter.”