S3 black screen and blue light

[C03BRA79]

Help!

My phone was rooted, I'm about to trade it in and tried to "unroot". Now when I turn on my phone I see "Samsung" then "Samsung galaxy s3" then the screen goes black it makes noises like its booting up and all I get is the blue light in the top left stays lit

I had "team epic" root installed and used their instructions to "unroot".

Any help would be greatly appreciated!