tweeted that his attorney general should stop the Mueller investigation?

Trump’s attorney general, Jeff Sessions, had recused himself from the investigation into Russian election interference, which developed into the Special Council after Trump fired FBI Director James Comey. Trump’s tweet that “Jeff Sessions should stop this Rigged Witch Hunt right now” was immediately called an example of attempting to obstruct the Special Council’s investigation.

New York Times – Trump Tells Sessions to ‘Stop This Rigged Witch Hunt Right Now’