"The whole tower; it's gone. ... Holy crap, they knocked the whole fricking thing down."
You can hear the anguish in a New York City police officer's voice as he watched from above when the World Trade Center towers started to come down on Sept. 11, 2001.
There's newly released video, taken from an NYPD helicopter, of the scene on that unforgettable day. It's "part of a cache of information from the attack handed over by city agencies to the National Institute of Standards and Technology, the federal agency that investigated the collapse," the Associated Press reports, and NIST has released it following a Freedom of Information Act request.
New York's Daily News has all 16+ minutes posted here. It is, as you might imagine, graphic. Among the other ways to see some of it is this video report from The Associated Press (9:25 a.m. ET note — earlier we had a video from Reuters; it appears to have been removed from YouTube):