Robert S. Mueller III, the former FBI director tapped by the Justice Department on Wednesday to be a special counsel overseeing the Russia investigation, has spent most of his life in public service.

Mueller, 72, was named to head the FBI one week before the Sept. 11, 2001 terror attacks – and spent the next 12 years at the helm of the agency, a tenure second in length only to J. Edgar Hoover.

At his confirmation hearings, Mueller vowed that his highest priority would be “to restore the public’s confidence in the FBI."

Mueller’s arrival to the FBI came after turbulent times that included the agency's deadly confrontation with Branch Davidians in Waco, Texas; the discovery of FBI agent-turned-Russian-spy Robert Hanssen; and the disclosure of documents withheld from lawyers representing convicted Oklahoma City bomber Timothy McVeigh. By many accounts, Mueller succeeded. When Mueller stepped down as FBI chief in 2013, he was praised by frequent FBI critic Sen. Chuck Grassley, R-Iowa., who called the New York City native “a great American.”

​Now, he has a new challenge: Overseeing the FBI's ongoing counterintelligence investigation into possible collusion between Trump campaign associates and Russia. His appointment comes after revelations earlier this week that the abruptly fired FBI director James Comey kept notes of a February meeting indicating Trump asked him to close the agency's investigation into former national security adviser Michael Flynn.

Those who know him say he's the ideal choice. "Bob Mueller is an outstanding choice because he is apolitical and follows the rule of law, and follows the evidence wherever it leads, regardless of political outcomes," said John Pistole, a former FBI deputy director, under Mueller.

Here are seven things to know about the man who will oversee the probe into the Trump campaign’s ties to Russia in last year’s election: