User blog comment:FairyRaven/Fairy Tail Chapter 392: You Must Not Forget, Review and Commentary/@comment-7418318-20140711094725/@comment-7418318-20140711102158

And we're back to the "Gray is a half-Demon" theories. ^^

That'd actually be a good explanation why Silver would force Gray to kill him, out of the guilt for killing his own wife, Gray's mother and their entire hometown, but rather than committing suicide, he decided that the one who suffered the most should do the deed.

I don't think Mashima will use this, but it would make sense.