My Samsung Galaxy S3 has a black screen
Before it flickered did you see any green light or something. I suspect the screen is cracked. Experienced it twice on my S3. Try to enter download mode, if nothing shows up there too then it probably is screen issue and not some kernel screw up. Also look for some cracks, in my case it was really tough to notice the cracks that caused a large hole in my pocket. 
Best of luck. I wish my inference is wrong.