The adjective "assassinated" (noun assassination) means killed for a political or social reason, rather than entirely for personal motives. Because this involves prominent individuals, the term is often questionably applied to killings of other famous people.
Historically, many world leaders have been assassinated, the majority because they stood in the way of some person or group obtaining power of their own.
Four US Presidents were assassinated : Lincoln, Garfield, McKinley, and Kennedy. Only Lincoln's death is indisputably considered a political act, by John Wilkes Booth acting along with other Southern sympathizers.