Historians and former Secret Service agents have created a documentary shedding new light on the JFK assassination.

MONTHS before the 50th anniversary of US President John F Kennedy's assassination, a retired Australian detective has suggested a US Secret Service agent fired one of the bullets that felled Kennedy.

JFK: The Smoking Gun is a television documentary based on the work of retired Australian police Detective Colin McLaren, who spent four years combing through evidence from Kennedy's death on November 22, 1963.

The two-hour docudrama will be broadcast in the US, Australia and Canada in November.

It suggests that agent George Hickey fired one of the bullets that hit Kennedy.

Hickey, who is now dead, was riding in the car behind Kennedy's limo that day.

It is not suggested Hickey was involved in a conspiracy, rather that he wasn't fit to be guarding the president as he had been out drinking with fellow agents the night before and was handling a firearm without adequate training.

The documentary suggests the firearm accidentally discharged when Hickey's car stopped suddenly after the first shots were fired by Oswald.

The program is ReelzChannel's second Kennedy-related offering. In 2011, the cable channel aired The Kennedys, after History Channel dropped the miniseries.

This story was updated on August 1 to clarify that Hickey's alleged shooting of Kennedy was believed to be accidental.

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