During the Warren Commission's investigation into the assassination of John F. Kennedy, the Commission received word via a backchannel that Fidel Castro, then Prime Minister of Cuba, wanted to talk to them. The Commission sent Coleman as an investigator and he met with Castro on a fishing boat off the coast of Cuba. Castro denied any involvement in the assassination of President Kennedy during Coleman's three-hour questioning. Coleman reported the results of his investigation and interview with Castro directly to Commission Chairman Earl Warren, the Chief Justice of the United States.