New helicopter footage of World Trade Center attack released (Natural sound)

New video of the September 11, 2001 attacks surfaced on Monday, from a police helicopter hovering near the burning World Trade Center towers in the hope of rescuing survivors from the rooftops.
"The whole tower, it's gone," one officer is heard yelling. "Holy crap, they knocked the whole fricking thing down."
The video is part of a cache of information from the attack handed over by city agencies to the National Institute of Standards and Technology (NIST), the federal agency that investigated the collapse.
The video surfaced on several websites Monday, but NIST did not know who posted it initially.
The 17 minutes of footage shot from a New York Police Department air and sea rescue chopper shows much of what has already been seen but still shocks and disturbs: a chilling aerial view of the burning twin towers and the apocalyptic shroud of smoke and dust that settled over the city.
Only police helicopters were allowed in the airspace near the skyscrapers, and the officers were the only ones shooting images from above.
The helicopter flies over the roof as huge gray clouds billow, and away as the video pans out to lower Manhattan. The video was released by NIST on March 3 under a Freedom of Information Act request, but it wasn't clear who published the footage online.
NIST investigated the collapse of the twin towers and another building that was part of the World Trade Center complex after the 2001 attacks.