My thoughts are with the family and friends, particularly the father, he will never be able to forgive himself.
I find it so hard to take that so many make it to the surface and then slip back under only to loose their lives.
A 30 minute dive, was he OOA? I would expect not, maybe low but no mention of an OOA situation.
A strong and fit teenager, he should have been able to swim any configuration to the surface.
However a mouthful of salt water at the wrong moment, a coughing fit, oveweighted, and regulator slipped behind him, maybe some scenario like that.
I hope that more info becomes available to allow us to understand the circumstances that resulted in this tragic accident and some useful lessons learned may come from it.