Rock the C.D.R.
There is nothing like a rock smashing through a window in the middle of the night to bring terror to a family. Attach a note to the rock, written with the non-hand writing hand. It can't be analyzed for identification of the writer and looks real spooky. Mind the fingerprints! The note should warn them that they should do nothing else to support Castro or the next thing that will crash through their window in the middle of the night will be filled with gasoline.