In an early scene of Back to the Future, Doc is
shot by the terrorists whom he 'scammed' the plutonium off of
It's feasible that the terrorists would be able to find out that Doc lived in Hill Valley. However, it seems mighty unlikely that they could figure out Doc's exact location and the time he was going to be there.
All we get in the movie is Doc muttering a bit about the fact that they found him and he doesn't know how.
So, my question is:
How did the terrorists determine Doc's exact whereabouts and when he would be there? I'm open to accepting any information from the producers outside the movie.