Newly released footage of the World Trade Center attacks shows an NYPD helicopter's perspective of that fated day.
The National Institute of Standards and Technology obtained the footage under the Freedom of Information Act as a part of their investigation into 9/11. The original footage was then anonymously posted onto Cryptome, a site which, among other things, catalogued the civilian deaths in Iraq, and posted protest photos in Libya.
The grainy footage swoops through the burning towers and captures the resultant collapse. It's an incredible new perspective of that day, but be warned: the footage is difficult to watch.