In the wake of President Trump’s firing of FBI Director James Comey last year, then-Acting FBI Director Andrew McCabe launched an obstruction-of-justice investigation—even before special counsel Robert Mueller was appointed, CNN reports. Sources cited by CNN said the probe had been under consideration before Trump dismissed Comey last May, in part due to the president’s conversation with Comey in which he reportedly urged an end to the investigation into former National Security Adviser Michael Flynn. Deputy Attorney General Rod Rosenstein and FBI officials reportedly had major concerns about Trump’s behavior at the time, and they discussed various options before the obstruction case was launched. Both Rosenstein and McCabe have been frequent targets of Trump on Twitter, with the president retweeting an image of Rosenstein behind bars just last week. McCabe was fired by Attorney General Jeff Sessions this year. The new details about the origins of the obstruction case against Trump came just a day before Mueller’s team is expected to provide court filings Friday involving Trump’s former campaign chairman Paul Manafort and former lawyer Michael Cohen.