I wonder precisely how technical the route was and whether or not this gentleman knew what he was getting into.
Canyoneering is a sport that does not suffer fools. It's very easy to put yourself in a position where you can not climb back up the way you came down & you may not be able to set proper anchors to rap out even if you have the right equipment.
I have little hesitation about undertaking a number of activities solo but canyoneering is not one of them. I'm >20 years this mans junior and in very good physical condition to boot.
I hope he makes a full and speedy recovery and I hope someone learns from this incident.