President William McKinley (who was assassinated) often wore a trademark good luck charm. It was a red carnation worn on his lapel. While meeting with the public a 12 year old girl asked him for the flower. He gave it to her and moments later was shot.

Assassination of William McKinley

On September 6, 1901, William McKinley, the 25th President of the United States, was shot on the grounds of the Pan-American Exposition at the Temple of Music in Buffalo, New York. He was shaking hands with the public when Leon Czolgosz, an anarchist, shot him twice in the abdomen. McKinley died eight days later on September 14 of gangrene caused by the gunshot wounds. He was the third American president to have been assassinated, following Abraham Lincoln in 1865 and James A. Garfield in 1881.

McKinley had been elected for a second term in 1900. He enjoyed meeting the public, and was reluctant to accept the security available to his office. Secretary to the President George B. Cortelyou feared that an assassination attempt would take p…
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Source: https://en.wikipedia.org/wiki/Assassination_of_William_McKinley#At_the_Temple_of_Music