It's an unfortunate situation, but your screenshot doesn't prove anything. I'm not defending OP, but without a proof of address (posted from his account here on the forums or in your screenshot), it's going to be hard for anyone to prove that it was actually him.

I personally want to believe you, but if you really want, try to get him red-tagged by creating a scam accusation with proper documentation and screenshots of the whole process of him scamming you and stealing your bitcoin.

Good luck.

And OP, if you're selling stolen bitcoin, fuck you. You're scum.