Robert S. Mueller III, a career prosecutor who became a central figure in two searing national traumas, first as FBI director in the aftermath of the 9/11 terrorist attacks and later as special counsel investigating ties between President Donald Trump’s campaign and Russia, died Friday. He was 81.

Mr. Mueller’s family confirmed his death in a statement Saturday to the Associated Press. Mr. Mueller had been diagnosed with Parkinson’s disease in 2021, according to a statement his family shared with the New York Times last year.

During more than four decades in law enforcement — as line prosecutor, U.S. attorney and FBI chief — Mr. Mueller developed a reputation as a stickler for detail who savored methodical investigation and nearly always got his man. Some colleagues privately spoke of the decorated Marine veteran as “Bobby Three Sticks,” referring to his patrician pedigree and the three-fingered Boy Scout salute.....

Mr. Mueller maintained a public silence through the 22 months of his Russia investigation, which yielded indictments leading to convictions of a Trump campaign chairman, a deputy campaign manager, a national security adviser and one of his personal attorneys.

In his report, released in April 2019, Mr. Mueller concluded that “the Russian government perceived it would benefit from a Trump presidency and worked to secure that outcome,” and that the Trump campaign “expected it would benefit electorally from information stolen and released through Russian efforts.”

Statement by President George W. Bush on the passing of Robert Mueller:

"Laura and I are deeply saddened by the loss of Robert Mueller. Bob dedicated his life to public service. As a Marine in Vietnam, he proved he was ready for tough assignments. He earned a Bronze Star and a Purple Heart before returning home to pursue law.

In 2001, only one week into the job as the 6th Director of the F.B.I., Bob transitioned the agency mission to protecting the homeland after September 11. He led the agency effectively, helping prevent another terrorist attack on U.S. soil. Laura and I send our heartfelt sympathy to his wife of nearly 60 years, Ann, and the Mueller family."