This is the World Trade Center attacks, as seen from an NYPD helicopter. I'm not sure I can do it justice, except to say that it's among the most transfixing 17 minutes of video I've ever seen. The clip was
originally obtained by the National Institute of Standards and Technology under the Freedom of Information Act for their investigation into the attacks, and anonymously sent, released, along with several still photographs taken from another helicopter, to the secret-sharing website Cryptome by the National Institute of Standards and Technology to fulfill a Freedom of Information Act request. You can download the photos here.