From the looks of it, the stone had been weak for quite some time, and, as he's a fair bit heavier than the ettercap, he provided just enough stress to finally finish the job. Below, he'll see what looks like a man-made structure, running perpendicular to the cave he's in now. The signs of a long-ago battle are visible along the walls; blood stains and broken arrows, and mostly rotted skeletons, scattered about the wide hallway, difficult to see through the several inches of brackish water on the floor.