Strangely, I first heard the rumor as early as the summer of 1968, before the Holy Grail of clues, better known as the "White Album", was released. At that time, there were precious few clues, and the rumor was (believe it or not) that Paul intended to kill himself, live on TV, on the "Ed Sullivan Show", to protest the Vietnam War. No, seriously.
It sounded like so much BS to me, I didn't even bother to do anything but laugh. I heard it from some students that attended the University of Wisconsin. Then, when the big story broke in 1969, I thought to myself, "Where have I heard this crap before?"