Robert Mueller had only been at the helm of the FBI for a week when terrorists successfully launched the biggest attack on U.S. soil since Pearl Harbor. Now, after 12 years of evolving threats against the United States, Mueller is preparing to say goodbye to the agency he has led for so long.
Even now, he loses sleep over what he described as the viable scenarios in which a terrorist could successfully take down a plane mid-flight, or biological weapons of mass destruction could fall into the hands of a terrorist or terrorist group.
However, he told "Power Players" that the recent threat that shuttered U.S. embassies overseas seems to have subsided.
"I think we have thwarted the initial attack plans, but we are monitoring the situation closely to determine whether there are still individuals out there that want to undertake much of the same or type of activity," Mueller told ABC News' Pierre Thomas in a rare interview.
Meanwhile, Mueller said FBI officials "areRead More »from FBI Director: Some U.S. citizens fighting in Syria, could pose future threat