911 video of planes hitting towers

In the moment, Mark LaGanga did not know. 

As the CBS News photojournalist drove down Manhattan's West Side Highway on September 11, 2001, he did not know he was headed toward the deadliest terrorist attack on American soil.

He was unaware that the south tower had already collapsed in on itself, and he could not have imagined the north tower would fall shortly thereafter, engulfing him and everyone around him in a thick cloud of ashen debris. 

All he knew was that he had to stay and film it. 

Twenty-three years after the September 11th terrorist attack, the footage LaGanga captured that morning provides a unique firsthand account of the rescue workers at ground zero moments after the two planes hit.

LaGanga's footage gives viewers a rare, up-close look at the 29 minutes of dust, confusion, and stillness in between the time the two World Trade Center towers collapsed.

"I saw the Twin Towers fall"

Earlier that morning, LaGanga's cellphone and home landline rang s