On the morning of September 11, 2001, firefighters who had been operating in and around the World Trade Center faced a cataclysmic event for which no training could prepare them. After the South Tower collapsed at 9:59 a.m., survivors and those still evacuating the North Tower described the sheer terror of witnessing the second collapse from the street level at 10:28 a.m. From their perspective on the ground, engulfed in deafening noise, blinding dust, and chaos, the building did not simply fall