Four US Presidents have been assassinated throughout history:
Abraham Lincoln - Lincoln was assassinated on April 14, 1865, by John Wilkes Booth at Ford's Theatre in Washington, D.C. This tragic event occurred just days after the end of the American Civil War.
James A. Garfield - Garfield was assassinated on July 2, 1881, by Charles J. Guiteau at the Baltimore and Potomac Railroad Station in Washington, D.C. Garfield's assassination was motivated by Guiteau's personal grievances.
William McKinley - McKinley was assassinated on September 6, 1901, by Leon Czolgosz at the Pan-American Exposition in Buffalo, New York. Czolgosz was an anarchist who opposed McKinley's policies.
John F. Kennedy - Kennedy was assassinated on November 22, 1963, in Dallas, Texas. Lee Harvey Oswald was charged with the assassination, although there have been various conspiracy theories surrounding the event.
These tragic events had a significant impact on American history and sparked widespread mourning and national reflection.
References:
History.com - Abraham Lincoln Assassination
History.com - James A. Garfield Assassination
History.com - William McKinley Assassination
History.com - John F. Kennedy Assassination