How Did Osama Bin Laden Really Die, If He Did?

Is was announced on May 1 that Osama bin Laden was killed by American intelligence operatives, but many haunting questions remain. Was it necessary to kill him? Was it even preferable or legal to do so? Was it in accordance with Islamic custom to bury him at sea? And, perhaps the most interesting question: How can we be so sure that it was bin Laden who was killed?