On 3rd December, 1963, the CIA received information that Gilberto Lopez, a Cuban-American, was involved in the assassination of JFK. Apparently, Lopez left America for Cuba the day after the assassination. This information was passed to the FBI but according to a CIA memo the bureau failed to investigate the matter (well, they never provided the CIA with any information on the subject). This is indeed a strange case as Gilberto Lopez had been a member of the Fair Play for Cuba Committee (FPC