It could be post-mortem changes, or trauma that caused the death. Without knowing the owner, or the situation, this can't be ruled out. Many times accidental placement of a rock hide or dish, causes trauma and it's so quick the owner doesn't see it happen. The snake crawls to a corner and dies unbeknowingly.

If there are any bugs in the enclosure this could be them feeding on the carcass. The face is a common place for this to first be seen.

SC worms generally aren't observed exiting in such a fashion; exceptions may be bot flies but you should see a large lump grow first as the maggot grows. I have not heard of these in snakes.

Ian