President Donald Trump Kevin Lamarque | Reuters

President Donald Trump spent his Thursday morning lashing out at the media, calling out reporters and news outlets by name and suggesting, apparently for the first time, that video of him explaining his decision to fire ex-FBI Director James Comey had been misleadingly presented. "When Lester Holt got caught fudging my tape on Russia, they were hurt badly!" Trump said of the "NBC Nightly News" host. Trump did not provide any evidence for his claim that Holt had manipulated the tape, and it was not clear what the president meant by saying Holt was "caught" altering it.

Trump tweet What's going on at CNN is happening, to different degrees, at other networks - with @NBCNews being the worst. The good news is that Andy Lack(y) is about to be fired(?) for incompetence, and much worse. When Lester Holt got caught fudging my tape on Russia, they were hurt badly! A spokesman for NBC News declined to comment. In a May 2017 interview just two days after he fired Comey, Trump told Holt he was thinking about the Russia probe when he made the decision. "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've won," Trump said in the interview. Watch the extended interview below.

The White House did not immediately respond to CNBC's request for comment. NBC News, like CNBC, is part of NBCUniversal. The president's social media fusillade dovetailed with recent news reports suggesting that Trump and his attorneys are adopting a siege mentality, as the potential threats loom from special counsel Robert Mueller's Russia probe, compounded by the potential for Democrats flipping the House in the midterm elections and the investigations they might launch. There's also the specter of impeachment, which Trump has discussed with his lawyers. Trump targeted several others during his Twitter tirade Thursday. Over the course of three hours, the president launched broadsides against CNN and its president, Jeff Zucker; NBC News chairman Andy Lack, Comey, Justice Department official Bruce Ohr and reports about the outgoing White House counsel, Don McGahn.

Mueller and the impeachment threat

The Washington Post reported Wednesday that Trump is considering new additions for both the White House counsel's office and his own personal legal team — including defense attorney Abbe Lowell, who represents Trump's son-in-law, Jared Kushner — to fortify his defenses against a possible impeachment fight should Democrats gain power in Congress. Read more: Trump's lawyers hope Emmet Flood will keep focus on Mueller, not replace White House counsel McGahn Trump's personal lawyers have weighed in publicly on the prospect of Democrats lodging articles of impeachment against Trump, although it's unclear what role, if any, they would play in such a probe. "Obviously it comes up, but it's not something on our mind right now," Trump's attorney, former New York Mayor Rudy Giuliani, told NBC News on Wednesday. As Trump's longtime friend and most outspoken lawyer, Giuliani has instead chosen to focus on crafting a rebuttal to what he anticipates will be a report published by Mueller at the conclusion of his investigation into Russian meddling during the 2016 presidential election. "We talk about impeachment from the point of view of: What are the steps we can take now to try to avoid it, to try to defeat it?" Giuliani told NBC. "The only thing you can do about it is try to make sure that whatever comes out in the report is rebutted properly. That's all you can do right now." It is not clear when or if Mueller will indeed issue such a report.

The McGahn factor

McGahn, whose departure Trump announced by tweet on Wednesday, has taken a less defensive stance toward Mueller's probe. While Giuliani and Trump's other outside lawyer, Jay Sekulow, have recently decried a potential face-to-face interview between Trump and Mueller as a "perjury trap," McGahn voluntarily sat for interviews with the special counsel totaling about 30 hours, The New York Times reported.

Trump said McGahn will leave his position following a confirmation vote on Supreme Court nominee Brett Kavanaugh. Trump's tweets about Holt and McGahn on Thursday signaled a greater focus on attacking Mueller in the context of an obstruction probe — rather than Mueller's other interest in potential coordination between Trump's campaign and the Kremlin. Trump tweet I am very excited about the person who will be taking the place of Don McGahn as White House Counsel! I liked Don, but he was NOT responsible for me not firing Bob Mueller or Jeff Sessions. So much Fake Reporting and Fake News! Still, he again slammed the "Rigged Russia Witch Hunt" in a tweet defending the staffing change, which Trump described as "my decision." Trump tweet The Rigged Russia Witch Hunt did not come into play, even a little bit, with respect to my decision on Don McGahn! A White House official, who declined to be named, told NBC News that Trump was referring to his decision to accept McGahn's resignation. In addition to McGahn's departure, about a third of the White House counsel's lawyers have departed the office in the past year and have yet to be replaced. This leaves about 25 lawyers total working in the counsel's office, according to The Washington Post, fewer than at any time in the past three decades. At the height of President Bill Clinton's legal battle with House Republicans in the late 1990s, for example, the counsel's office employed as many as 60 lawyers to oversee the president's defense.

More Trump targets

WATCH: Former Republican James Comey urges Americans to vote for Dems in midterms