It's been 20 years since the 9/11 terror attack on the Twin Towers at the World Trade Centre. 

2,977 people lost their lives that day, including 343 firefighters. 

Chief Joseph Pfeifer was the first FDNY chief to arrive at the twin towers and took command of the rescue operation in the north tower. 

Chief Pfeifer has detailed the day and its impact in a new book Ordinary Heroes: A Memoir of 9/11. The book is available now.

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