From the sworn testimony in the case: The lake was flat "like glass" when the divers went in, with 20-30 foot of visibility. While they were underwater, the winds picked up unexpectedly and were blowing hard, creating 2-3 foot seas with whitecaps while they were underwater. When the adult made a sudden, unexpected and uncontrolled ascent to the surface, the instructor looked up from 14 ft., saw the surface conditions (with waves that were over the divers head), and determined that it was unsafe to have three inexperienced divers on the surface in these conditions. So he signaled for the boys to stop and wait on the bottom, ascended 14 ft to the surface, asked the adult diver if he was okay and immediately took him back down. The whole thing took just 25 seconds from bottom to top and back down again.
However, shortly after the instructor went up, the boy that died gave the "up" signal to the other boy and started to ascend. Not wanting to be left alone, the other boy followed. They did not turn around to look to see where the instructor and other diver were. They ascended to the surface but one boy stopped a few feet short. The other boy looked back down, saw DT hovering below the surface within arm's reach, with his regulator out and bubbles escaping from his mouth. The boy tried to bring DT to the surface but he was non-responsive. Eventually, DT sank back down to the bottom. The waves were such that boy could not see shore, but he could see a flag on a flag pole on a platform near shore, so he swam to this and then he was helped back to the dock.
These are the facts according to the testimony of the witnesses who were there. Now, have at it.