My level of sympathy for this person is low, given that they did this to themselves.
I personally have never understood the attraction of drugs or alcohol for enjoying what life offers, especially when you have so much wealth that you can literally spend the rest of your life travelling to see the world and still not have enough time to see it all!
As a Prince, he was living the life that all of us can only imagine, and he decided to risk it all on drugs and alcohol. Go figure.
Condolences to his family though.