Well, based on what we now know I now feel quite certain that Rory Williams is the good man that River "kills".
Knowing that both Amy and his unborn child has been abducted is bound to drive Rory nuts. I bet he would do anything to rescue mother and child. And for some yet unknown reason, this results in him getting "killed" by River Song.
I am putting "killed" in quotes because I believe River Song lies just like The Doctor (This would be a good chance for The Doctor to plant River Song with the idea that he lies, giving River the clue she needed to realize that he isn't really dead back in "The Big Bang"). My belief is that The Doctor needed the universe to believe that Rory is dead, so they faked Rory's death and River Song willing goes to jail for the crime. Of course, this is just my wild guess