I've been a Prince fan for along time, and that is his voice...
As for when the recording was made I don't know, but I can't really see him making a comment like that after 9-11...
He has always been rather opinionated (the song Ronnie Talk to Russia comes to mind) and he is something of a conspiracy guy as well (look up the Tavis Smiley Prince interview about chemtrails) so I don't find it too difficult to believe that he may have seen something...