The Barry Seal story was made into a movie called "Double-crossed" with Dennis Hopper playing the lead role. Quite a good movie (some interesting flying scenes) and pretty amazing if only half true!
In the movie Barry Seal became an FBI agent and assisted in the exposure of drug smuggling at high levels of the government in Columbia. In the end a judge in the US welched on a deal the FBI had promised Seal, and he was sent to a 'half-way house' type detention center where the smugglers got to him and shot him dead.
Don't know anything about the other man you mentioned.