It wasn't clear whether the president was basing his tweet on direct knowledge that he is under investigation, or on reports this week that special counsel Robert Mueller is examining whether the president obstructed justice by firing Comey last month amid the ongoing Russian Federation investigation.
The memo from the transition's general counsel directs all staffers and volunteers who worked on the Trump transition to "preserve any written documents.as well as any electronic information" related to Russia, Ukraine and any foreign travel by Trump transition members.
Trump also seemed to confirm reports in the Washington Post and other publications that Mueller's investigation has expanded to include allegations that he attempted to obstruct the ongoing investigation into Russian meddling in the election and his campaign associates' possible collusion with Russians.
The president wrote on Twitter Friday: "I am being investigated for firing the FBI Director by the man who told me to fire the FBI Director!"
The comment came after the president tweeted on Friday: "I am being investigated for firing the FBI Director by the man who told me to fire the FBI Director!"
Under federal rules, Trump can't fire Mueller. During an interview with NBC two days later, Trump said he fired Comey because "this Russian Federation thing with Trump and Russian Federation is a made-up story". "That the president was not and is not a target of investigation".
Rosenstein took command of the investigation in early March, when Sessions announced that he was recusing himself due to his substantial role in Trump's presidential campaign a year ago. According to the White House, Trump had met on May 8 with Rosenstein and Sessions, who told their boss then they had concerns about Comey. But regardless of recommendation, I was going to fire Comey. Robert Mueller reports to Rosenstein, but is authorized to pursue the investigation independently.More news: London fire toll hits 30, but dozens missing
But any involvement of Rosenstein - who himself only took over the probe after Sessions recused himself - is complicated by the fact that he authored the memo that Trump cited in terminating Comey. The committee also sent a letter to Comey asking for any notes or memos.
Rosenstein now has such authority because Attorney General Jeff Sessions recused himself on 2 March after revelations of previously undisclosed meetings with Russia's ambassador to Washington while he was a Trump campaign advisor.
"Crooked H destroyed phones w/ hammer, "bleached" emails, & had husband meet w/AG days before she was cleared - & they talk about obstruction?" he wrote.
"That signifies this president knew all too well that it was inappropriate", Schiff said.
In the Senate, Sen. King said the "collusion, the cooperation aspect of the investigation is not over".
Donald Trump, for your refusal to stop digging yourself into a hole, you had the Worst Week in Washington.
Aides have counseled the president to stay off Twitter and focus on other aspects of his job.