Ya it's very confusing....
But, I'll bet that the second diver who happend along this OOA diver HAD a working second stage but was unable to switch to it.
Here's my guess:
The guy that died had a free flow or a malfuntion and the other guy shows up and there is panic.
The second diver has some horrrible octo rig or something, his primary is a short hose. He hasn't practiced an OOA situtation in a while (maybe not since his OW), he donates (or the OOA diver grabs) his primary, the donator is panicing, he can't find his secondary, the OOA is so close to him and is panicing too, it's cold, it's dark, and with the deep breaths the nacrosis kicks in. All of sudden the donators is holding his breath a little bit, he's postivley bouyant, he's really losing his cool, he's shooting up.
Then back on the boat he realizes that 100' in cold, dark water isn't a piece of cake when something goes wrong.
This wreck is so popular that people think it's an "easy" dive, they think that 100' is shallow, that think they don't get narced at that depth. It is a great wreck (and the inside is even better), but, just because top tech dives can do 400', 100' is still deep under these conditions and needs to be treated with respect and caution.
Donating air needs to basic skill that you practice over and over again, all this crap about sharing air on a short hose and swimming up from 100' and NOT have a bungeed reg right under your chin is BS.
If you want to dive wreck like this you need to TRAIN.