Five decades after the death of President John F. Kennedy, many still don't agree with the official record that Lee Harvey Oswald was the lone gunman in his assassination. Here are some of the most talked about conspiracy theories surrounding his death:

1) The CIA

The Central Intelligence Agency may have played a role in his death. The motive? The CIA was upset about the changes being made within the agency after the failed Bay of Pigs invasion. The CIA also did not want Kennedy to discharge CIA agents for disagreeing with him. Other theories pin the assassination on a rogue cell of the CIA or an agency contract killer gone rogue.

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The theory of forensic historian Patrick Nolan, whose book CIA Rogues and the Killing of the Kennedys asserts four high-level agents planned the shooting and three fired four shots in Dallas that day.

2) The Mafia

The Mafia may have killed Kennedy for several reasons. One being that the Mob was angry with brother Robert Kennedy efforts to crack down on organized crime. Another involves a theory that the Mafia was working with anti-Castro exile groups that were trying to take down JFK.

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3) The Soviets

The Cuban Missile Crisis in 1962 gave the Soviet security agency KGB very good reasons not to like Kennedy. Many say Oswald had a fascination with Russia after marrying a Russian woman, and he may have been acting as a KGB operative.

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4) Lyndon Johnson

Author Craig Zirbel argues that Vice President Johnson was motivated by political gain to organize Kennedy's assassination. Kennedy and Johnson had many political differences and personal issues. (Johnson may have been taken off of the Democratic ticket for Kennedy's re-election in 1964).

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The argument goes that Johnson's financial scandal and desire to be president served as possible reasons. Since Kennedy was visiting Texas, Johnson's home state, it seemed logical that Johnson could been involved. His associates also controlled many of the trip's details.

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5) Two shooters

The idea that there could have been a second shooter has been discussed often in intellectual circles. Some believe the shooter was hiding on a grassy knoll behind a picket fence that was located to the right of JFK's vehicle. Oswald could have fired a first shot from his perch in the Bookstore Depository, and then a second shooter fired.

6) The debunked umbrella man theory

Bill O'Reilly reported for WFSB that a man fired a dart from the tip of his umbrella at JFK. Theorists believed the umbrella man shot Kennedy in the neck. The theory was debunked in the late 1970s.