Strange, but it sounds like he may have been suffering from some kind of medical issues as well... since these guys were carrying reserve tanks etc, and clearly diving with other experienced divers, it's likely that they all did the right things in the situation. Most good, experienced divers are very methodical and careful when a situation arises. The problem is that in a true emergency, you tend to freak out - which is why most of the basic dive certification revolves around various emergency situations.. You really just practice having something bad happen to you, so that hopefully when it happens in real life, you know how to calmly deal with it. Just as a for instance, if you're swimming around following your buddy, it's inevitable that one of these times his/her flipper will catch you in the face and either rip off your mask or yank your regulator out of your mouth. The first time it happens, it's really unnerving - but after you've been diving a while, it is much less of a big deal - you just stop, think, and take very deliberate actions to fix the situation.