Robert Mueller's 12-year tenure heading the FBI, which started just before the Sept. 11, 2001, terror attacks, apparently will end his career amid questions about the FBI handling of another terror incident, how the Boston Marathon bombing suspects slipped away, says the New York Times. His privileged roots and sometimes wooden personality have not made him a beloved figure in the FBI's beer-and-brats culture, but he has always had supporters in both parties in Congress. “If an attack of this scale happens toward the end of your tenure and there is evidence that the FBI had its hands on the people years ago and missed them, that is what people will remember,” said Julian Zelizer, a Princeton historian and author of a book on the politics of national security. In the FBI, where agents check out the smallest terrorist tip and have built databases of millions of names, the view was that it was only a matter of time before the agency would be blamed for the next attack. From the agents' perspective, the FBI is vigilant, not incompetent. “In some ways, they're a victim of their own success,” said Kenneth Wainstein, a former chief of staff to Mueller and former general counsel at the FBI.