Four Presidents of the United States of America were assassinated.
Lincoln's assassination was the first of any US president and took place during the years of the American Civil War. It took place on the 14th April 1865 at Ford's Theatre in Washington. He shot at close range in the presidential box by John Wilkes Booth, an actor.
Garfield, second president to be assassinated, was shot and mortally wounded whilst waiting at train station. He was shot by Charles Julius Guiteau. The bullet that killed him was hidden from the doctors trying to save them and Alexander Graham Bell invented a metal detector to try to find it.
McKinley, was shot and killed at close range at the 1901 Pan-American exposition by Leon Czolgosz.
Kennedy. Officially, Kennedy (the most famous dead President?) was shot at long range by a US trained sniper, Lee Harvey Oswald in Dallas. Conspiracy theories abound that he was killed by the Soviets, the Mob and elements inside the US Government.