Incidents such as this one are caused in the vast majority of cases by a series of small breaks in the system... in this case, these divers exceeded their training, began their dive with the wrong attitude (signed a form saying they would not exceed 18 metres / 60 feet depth and choosing to ignore it), did not do an adequate buddy check on the surface (fouled octo and gas not fully turned on), ignored the training one of them had at least and did not do a a bubble check and S-drill at 10 feet (this would have shown up the octo problem... and remember one of them was cavern certified... they teach s-drills at that level), and seemed to have insufficient skills to avoid and then deal with a rather ordinary emergency (two things... the dead guy's SPG was probably fluttering throughout his dive, which had he enjoyed ANY level of situational awareness would have triggered a little reg flag for him; and secondly, the victim did not attempt a CESA... I do not agree with the practice but in this case, he should have dropped his weight belt and tried it perhaps).
One death, one guy scared for the rest of his life... and probably scared ****less that his arse is gonna get sued. And all because neither had ever realized that if you **** around with this stuff, make no mistake, you will die.