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Alice Hoglan (second from right) responds to questions about her son, Mark Bingham, who phoned her from United Airlines Flight 93 before it crashed near Shanksville. Bingham was one of the passengers who rose up against the terrorists on the doomed flight. Bingham's boyfriend of six years, Paul Holm, later expressed no surprise that Bingham risked his life to protect others, saying that his partner had twice saved him from attempted muggings -- including one at gunpoint. (Photo: JOHN G. MABANGLO/AFP/Getty Images)

For the full photo collection, go to LIFE.com

Confronting Terror: Faces of 9/11

Among the most eloquent and unsettling of the countless photographs from September 11, 2011, are those focusing not on the fall of the towers, or the jagged, smoking hole in the Pentagon, but on faces. Human faces etched with shock, fear, and disbelief at the cataclysm unfolding above them, or staring glassy-eyed into some unseen distance, stunned by the enormity of the barbarous terror unleashed that cloudless, late-summer morning. Here, LIFE.com presents a gallery focusing on witnesses to terror as they confront the unspeakable.