Robert Mueller had a long legal career when he was appointed special counsel in 2017 to investigate "the Russian government's efforts to influence the 2016 U.S. presidential election and related matters."
The investigations, which lasted for several years and particularly angered Donald Trump, showed that Russia influenced the 2016 presidential election. But only one person in the president's inner circle, national security adviser Michael Flynn, was formally charged.
Since the investigation began, Trump has repeatedly claimed that he has been the victim of a witch hunt and wrote on Truth Social after Mueller's death became known:
"Good. I'm glad he's dead. Now he can no longer harm innocent people."
Robert Mueller served as director of the Federal Bureau of Investigation (FBI) for 12 years. He was appointed by President George W. Bush in 2001 and took office just a week before the September 11 attacks on the United States.
He thus gained a central role in the domestic hunt for those responsible for the terrorist attack, and ensured that the FBI changed its focus in 2002 from primarily investigating serious crimes to acting "preventively" to stop planned terrorist acts against the United States or American interests.
He also had experience with terrorist acts in a previous role, when he led the investigation that in 1991 identified the later-convicted Libyan Abd al-Basit al-Megrahi as guilty of the Lockerbie attack in 1988.
Robert Mueller was 81.
