From the Mueller report (vol. 2, pp.158):
In considering the full scope of the conduct we investigated, the President's actions can
be divided into two distinct phases reflecting a possible shift in the President's motives. In the first phase , before the President fired Comey, the President had been assured that the FBI had not opened an investigation of him personally. The President deemed it critically important to make public that he was not under investigation, and he included that information in his termination letter to Comey after other efforts to have that information disclosed were unsuccessful.
Soon after he fired Comey, however, the President became aware that investigators were
conducting an obstruction-of-justice inquiry into his own conduct. That awareness marked a significant change in the President's conduct and the start of a second phase of action. The President launched public attacks on the investigation and individuals involved in it who could possess evidence adverse to the President, while in private, the President engaged in a series of targeted efforts to control the investigation. For instance, the President attempted to remove the Special Counsel; he sought to have Attorney General Sessions unrecuse himself and limit the investigation; he sought to prevent public disclosure of information about the June 9, 2016 meeting between Russians and campaign officials; and he used public forums to attack potential witnesses who might offer adverse information and to praise witnesses who declined to cooperate with the
government. Judgments about the nature of the President's motives during each phase would be informed by the totality of the evidence.
