Simorai was also examining the waterfall (standing near/next to Buckthorn?). Assuming he can, Simorai tries to Grab the clumsy fool before he falls (Dex check? - 24).
If he is not within reach or the Grab fails, he does the following. Despite his better judgment, instinctively his Loyal Unto Death (encounter power, ally within 10) training kicks in (curse his elite Janissary training in the service of the Sultan), teleporting him to swap places with Buckthorn (thinking, as he is falling but providing little comfort, that in his blooded state Buckthorn may not survive the fall and hoping that the teleport 10 squares will reduce the fall/damage on Simorai).