Even days without a terrorist attack, though, can be especially hard for the FBI director.
"The [other] most difficult days are when you lose your people," Mueller said, adding that "day in, day out" FBI agents "put their lives on the line" for their fellow Americans.
After graduating Princeton University in 1966, Mueller joined the United States Marine Corps and led a rifle platoon of the Third Marine Division in Vietnam. His dedication and courage earned him a Bronze Star, two Navy Commendation Medals, the Purple Heart and the Vietnamese Cross of Gallantry, according to an FBI profile.
Mueller then worked as a litigator in San Francisco and served 12 years as a federal prosecutor. (He received his J.D. from the University of Virginia.) A move to a private law firm in Boston ended when he began working in the Justice Department in Washington in 1989. Four years later, he briefly returned to the private sector before joining the U.S. Attorney's Office in Washington as a homicide prosecutor.
Mueller and his wife, Ann, have two daughters.