Former FBI director Robert Mueller has died at the age of 81 after a career defined by his leadership during the September 11 attacks and the Russia inquiry.He transformed the bureau into a counterterrorism force before serving as special counsel to investigate interference in the 2016 presidential election.The inquiry led by Mueller resulted in charges against six associates of Donald Trump though it did not conclude that a criminal conspiracy existed.Donald Trump reacted to the news with hostile social media comments as the family of the decorated Vietnam veteran requested privacy during this time.