We all know that Christian died in Australia before ending up on the island in the coffin. The question is - how did he die? All we know was that he was an alcoholic and then somehow he was dead and Jack had to come get the body. My theory is that he was murdered and maybe it was done by Ben in order to get the ball rolling on the events that would follow.
Think about Ben's interaction with Locke when he was about to commit suicide. He talked lock out of hanging himself only to murder him minutes after. Yes, it did seem that Locke mentioning Mrs. Hawking was part of the reason for doing so but maybe that was done that way just to throw us off. Maybe Ben had to murder Locke in order to keep the circumstances as similar as possible to the original flight?