I looked up the other pictures from this scene, and you know what? They both looked kinda happy together. Albeit he looked a bit flustered by the attention and possibly a bit hungover :-)
A photo just an instant. I've seen so many shots where people odd faces in situations. It doesn't mean anything.
I know it's shocking, but I suspect that in spite of the complications they actually quite loved each other, and that he killed himself for his own reasons. Moreover, I suspect he'd be pretty pissed off with some of his fans for blaming her.
Mind you, it makes it much easier for you to deal with it if you have a figure of hate that you can blame, doesn't it?