Newly released photographs show what a damaged World Trade Center tower and its collapse looked like from a New York Police Department helicopter as it flew nearby on September 11, 2001, in New York.
The aerial photos were obtained by ABC News after it filed a Freedom of Information Act request last year with the National Institute of Standards and Technology, which had collected the images for its investigation into the towers' collapse.
A couple of the images show one of the twin towers burning after a hijacked airplane had flown into it. Others show it collapsing, and the rest show the clouds of debris and dust spreading below after the towers crumbled.
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