John Brennan is pictured in the top right corner of this photograph. US Department of Defense

John Brennan, the former director of the CIA, told Business Insider that participating in planning the raid that killed former Al Qaeda leader Osama bin Laden was one of his proudest moments at the agency post-9/11.

Brennan was then-President Barack Obama's assistant for counterterrorism at the time of Operation Neptune Spear, which took place in May 2011, and he worked closely with the CIA and Special Forces.

Brennan said that the 72-hour period of time that he was in the Situation Room as the mission was carried out "was quite, quite intense as we went up to the point of bin Laden's takedown."

He added that the "minutes seemed like hours, it went on and on, and even after we knew that it seemed like the raid was successful, waiting for our forces ... to get out of Pakistani airspace safely ... it was white knuckles, because you always want to be able to succeed in your mission but you also want to make sure that the people who are undertaking these great risks and doing it are going to come home safely."

The raid was carried out by the elite SEAL Team Six after the US received intelligence that bin Laden was hiding out at his compound in Abbottabad, Pakistan.

Brennan told Business Insider that although there were many other proud moments he would like to talk about, he can't do so because "what is typical about the agency is that the successes are ones that you cannot tout and you don't see on the front pages."