I know what you mean, a really strange mix of weird and depressed mixed together. It is same as the feeling I had after watching One Hour Photo, amplified many times over. I think it was the fact that he seemed to be the guy that seemed like he genuinely had a huge love of life; and he was very emotionally contagious.
We just lost Mrs Doubtfire, Patch Adams, the voice of Genie, John Keating, Peter Pan, and the psychologist from Good Will Hunting all in one self inflicted action. Not to mention one of the funniest standups of our time, loving father who promoted Zelda Ocarina of Time with his daughter named after the Princess. All around appeared a really fantastic guy. Robin Williams is one of those rare celebrities where it is difficult not to feel anything but joy to see him on the screen; except in One Hour Photo. That's why it's a little weird and painful at the same time to see that face which he showed us defeated by a demon like depression; presumably.
Regardless of how he died, no doubt it would have still been a very sad day. His depression is at an end, the one way he knew how to end it. At least we'll still have his movies, his comedy, his interviews, and more.
-Insert Inspiring Quote-