That is the same choice I would make. Some will say that it is cowardice to end life instead of continuing. For me it is more about being a burden on someone to care for me, and the fact that I wouldn't truly be living if I were paralyzed.
That is why I have a living will, and my family knows my wishes.
Yes, he should have been wearing a harness. But it may be possible that he fell while climbing up to the stand when he fell.