Buddha story

The story goes: "In a past life, the Buddha was once told that a certain man was going to sink a ferry carrying five hundred people.  He prayed and reflected on what to do.  Should he kill the man to save five huindred lives? Or should he remain non-vioent, but allow those five hundred people to die? Finally he chose to kill the man, but not just to save all those lives.  He killed the man for the man's own sake, to save him from the karma of committing five hundred murders. He created good karma by committing murder with the best of intentions. He did not creats feelings or thoughts of guilt, which would have created bad karma, but acted with intention and compassion for all: the five hundred men, the would-be murderer and himself" (taken from the book, "The Eleven Eternal Principals")
Does this help to understand karma?
What does it say about our attitude to asylum seekers who risk their lives to come to Australia on leaky boats? Anything?
Food for thought, at least!