I know nothing about this incident, but I have had first aid training with CPR (it was required for my Rescue Diver training, and I've allowed my certification to lapse). It is worth being aware that the efficacy of CPR is considerably lower that most people know, and the farther away you are from professional medical help (e.g. at a dive site in the woods or on a dive boat) the worse the odds of a positive outcome are. Good skill to have? Probably. But no one should beat themselves up for not knowing it -- even administered by a trained bystander in the field, the odds of a positive outcome are minimal.
https://www.npr.org/sections/health-...n-enduring-cpr