The tweet said Trump fired former national security adviser Mike Flynn because Flynn lied to the FBI.
That'd be an issue because the day after Flynn resigned from the Trump administration, the president allegedly asked James Comey, then director of the FBI, to drop an investigation into Flynn.
Experts say if Trump had known Flynn lied to the FBI before he left the administration, that request to Comey could have amounted to obstruction of justice.
But Trump's personal lawyer, John Dowd, says he penned the tweet. Not only that, but he reportedly messed up the meaning. Sources told CBS that Dowd meant to say Flynn was fired and "now we know" he lied to the FBI.
Trump, or someone claiming to be Trump on his Twitter, took the defense further on Sunday, tweeting, "I never asked Comey to stop investigating Flynn."
The White House has long denied that Trump asked to halt the investigation. But Comey says he took detailed notes of his conversations with Trump, some of which reportedly indicate the request happened.