the force.net reported a spy report from a "reliable source" that that aurra sing, not tusken raiders, kill shmi. they didn't come out and say it, but hinted around that palpatine sent aurra to kill shmi for two reasons, 1. to draw anakin and padme out of hiding and, 2. to open the door for anakin's turn to the dark side.

they also didn't say it, but reading through the lines, they, like some have done here in the past, speculate that palpatine is anakins father.