Samsung Galaxy s3 Screen frozen

[AC Question]

I had a Samsung Galaxy S3. I was using it for the past 4 months ( second hand ). Today when I was using Facebook, All of a sudden my Mobile hanged. Just like normally S3 hangs. I pulled of the battery and restarted the phone. A green Glittery Screen appeared. I kept it in my freezer for some time. The screen changed from green to white. I don't know whats the matter and I couldn't find any thing useful over internet. Please can anyone help me with this issue. Has anyone else faced this issue before? Thanks in Advance. !