Who killed the Shah of Iran?

Shah Mohammed Reza Pahlavi was overthrown in the course of the Iranian Revolution of 1979 (also called the Islamic Revolution) and lived in exile. He lived out the remainder of his life in Egypt before he died from complications of Waldenström's macroglobulinemia (a type of non-Hodgkin lymphoma) on July 27, 1980. He was 60 years old.

Had he been handed over to Iran after the Revolution, he likely would have been executed.