Somewhere else I read that the inflator hose was not hooked up. But that piece of information seemed strange to me, since it would be hard to detect, unless someone was very close and presumably if they were that close, then they could have recovered him. Plus if someone saw it on the boat, it probably would have been fixed before entry.
Having the tank valve off and the BC not inflating, makes more sense to me.
So brother was with him, saw he was in trouble, victim ripped reg from mouth of brother, he freaks and bails on his brother and then the victim sinks in an over weighted condition, with no ditchable lead? Is that the scenario? That could happen in less than 30 seconds.
I am surprised the boat operator could not mark the position (MOB) to facilitate the recovery divers to find the victim. Surely the diver would be close to where he started his over weighted descent?
Where there DM's in the water? Did the operator begin an underwater search right away or were other divers down already and unaware, so any search would necessarily be delayed?