Did the deceased dive the Doria on Air (on occasion or regularly)?
If so, yeah sure, damn stupid cowboy style and an accident waiting to happen and that MAY explain why ALLEGEDLY the deceased had brought an O2 marked bottle filled with Air to a Doria trip and the same bottle killed him later in the cave dive we discuss here (but then why did he not use that "Air" bottle on the Doria trip and die then and there because as we know it was instead filled with O2... the mystery thickens).
He went to dive the Doria. he took 2 deco stages of O2 because they were planning 2 dives. Dive one went okay, used up deco stage of O2. Dive 2 was blown out, so did not use 2nd deco stage of O2.
Went back to Canada and filled empty ali 80, which was permanently marked for O2, with air. Went to Florida and grabbed wrong ali 80 (the one filled with O2) before leaving the house. Did not analyse gas before hitting the water and Oxtoxed.