It is sad what happened. No matter of the training anyone has we are all acceptable to accidents or death. I work in law enforcement. I own my own security guard company and have witnessed officers do stupid things. It's part of life. We all learn no one is perfect or exempt from an accident or death.
By the way. Don't most BC have a lever or string you can pull to release your weights. I know that the new BC are equip with them. Check out the new Zeagal and Atomic BC.
I read an article in the Scuba mag where an experience dive master took a dive trip and died. He was also out of shape and has not dove in years. He should have taken a refresher course. The dive went well until the end of the dive. The anchor was not coming up. So he dove in to guide the anchor to the boat and instead of holding on to the chain to ascend he was using all of his strength to rise. He was running out of air and with his bad health he couldn't make it up and panicked. He tried to remove his dive belt but the formidable happened and died. The boat crew tried to resuscitate him but had no luck.
“Remember we are all acceptable to injury or death.”