ABC News has learned that the Navy Seals who carried out the mission were using a top secret weapon -- the world's first stealth helicopter.
The fire that has been pictured burning at the compound where bin Laden was killed was meant to destroy evidence of one of the U.S. military's most closely guarded secrets: a stealth helicopter.
Former White House counterterrorism official Richard Clarke told ABC News: "For the Seals to go in and not be detected by Pakistani radar, the stealth helicopter was essential."
But after the fire, several large pieces of the U.S. chopper remained. Aviation analysts say they provide the first real evidence of a stealth Blackhawk helicopter whose existence had only been rumored.
The telltale signs are several modifications to key components of a standard Blackhawk helicopter.
" One of the things that really stands out," said Daniel Goure of the Lexington Institute, "is they have a little disk over the motors which is meant to baffle the sound and deny radar signature."
Neighbors in Abbotabad told ABC News they did not hear the helicopters Sunday night until they were directly overhead.
"It would be a vague sound," Goure said, explaining that it probably sound like "a helicopter that was going in the opposite direction."
In other pictures from the scene, children can be seen collecting the secret, fabric-like material that is used to make the chopper.
"There are probably people in the Pentagon," added Clarke, "who are very concerned that pieces of the helicopter may be, even now, on their way to China. Because we know that China is trying to make stealth aircraft."
The Chinese military has a close relationship with Pakistan and the remaining large pieces of the secret U.S. helicopter, some hidden under a tarp, were trucked away by Pakistani officials Tuesday to an unknown destination.
