Whatever happened to Radagast ?

[SilverToungedDevil]

At the end of the book, "The Grey Havens", when the great and wise leave ME, there is no Radagast. Where was he then? In "The Ring Goes South ", when the scouts are sent out prior to the Fellowship leaving Rivendell, it is reported that :

reached the old home of Radagast at Rhosgobel. Radagast was not there;

Also the words of Saruman ( "The Council of Elrond" ) come to mind :

"Radagast the Brown!" laughed Saruman, and he no longer concealed his scorn. "Radagast the Bird-tamer! Radagast the Simple! Radagast the Fool! Yet he had just the wit to play the part that I sent him"

Did Saruman have him murdered ? There just seems to be no sign of him anywhere later in the book. Again where did he go ?
Personally I think he was killed after he delivered the message to Gandalf. It would also be a sign of how much Saruman had fallen, having one of his own brother wizards murdered.