2 May 2011 Last updated at 16:11 ET
Speaking at a news conference he said that "the minutes passed like days" as senior governmnet officials watched events unfold.
Mr Brennan also told journalists that at one point in the operation a woman was used as a human shield to protect Bin Laden from incoming fire.
Inside the compound where Bin Laden was found
Bin Laden is believed to be the mastermind of the attacks on New York and Washington on 11 September 2001 and a number of others.
He was killed in a ground operation at the compound where he was hiding, in the town of Abbottabad.
Footage from inside the building showed scenes of disarray, and bloodstains on the floor. Steve Kingstone reports.
Footage courtesy of ABC News