He has often announced major staff changes on Twitter, catching the ousted aides off guard, among them former Chief of Staff Reince Priebus, National Security Advisor H.R. McMaster, Secretary of State Rex Tillerson and, just this week, White House counsel Donald McGahn. Trump tweeted that McGahn would depart this fall. Yet, often the president has humiliated senior advisors in tweets, comments and private asides — Atty. Gen. Jeff Sessions, in particular — while stopping short of firing them.