In this Feb. 1, 1968, file photo, South Vietnamese Gen. Nguyen Ngoc Loan, chief of the National Police, fires his pistol into the head of suspected Viet Cong officer Nguyen Van Lem (also known as Bay Lop) on a Saigon street, early in the Tet Offensive. The photo showed the war's brutality in a way Americans hadn't seen before. Protesters saw it as graphic evidence that the U.S. was fighting on the side of an unjust government. (AP Photo/Eddie Adams, File)
NEW YORK — It was a fraction of a second that jolted Americans’ view of the Vietnam War.