Robert Mueller, who has been appointed to handle the investigation into Russian meddling in the 2016 election, took the reins as FBI director a week before the attacks on Sept. 11, 2001. That day would influence his entire 12-year run leading the agency.
Mueller oversaw arguably the most significant changes the century-old FBI had ever gone through, and he received praise from lawmakers in both parties on Wednesday for his commitment to justice.
"I had been a prosecutor before, so I anticipated spending time on public corruption cases and narcotics cases and bank robberies and the like," he told NPR in 2013. "And Sept. 11 changed all of that."
Mueller overhauled the agency to prioritize, first, the threat of terrorism from groups like al-Qaida and the Taliban, and then later, the threat from individuals not affiliated with any particular group, like the Tsarnaev brothers.
He moved thousands of agents from criminal investigations into counterterrorism and national security. He detailed the changes in 2003, at an American Civil Liberties Union conference: