President William McKinley gave a speech at the Pan American Exposition in Buffalo, New York, on September 5, 1901. The next day, while attending a reception, an anarchist named Leon F. Czolgosz went to shake hands with McKinley. Czolgosz fired two bullets at the President with a revolver concealed by a handkerchief in his right hand. An ambulance rushed President McKinley to the hospital for emergency surgery. McKinley seemed to be recovering for a while, but he died on September 14, 1901.
The killer, Leon Czolgosz, who was probably insane thought the President "Was an enemy of good working people ". There was a world-wide anarchy movement active at around that time. ( see the related link)