So my friend was trying to use kingo root to root his GS3 and his dog ran and got unplugged during the process, is he f*cked?
EDIT: Used odin and flash a custom recovery after his was borked, got him on a custom rom and flashing him back to stock to use as a backup. Was kinda a mess but it cleared up, took a couple hours but got it, sorry for the random forum post.
You really have not provided to much information.
Does the phone restart if you hold the power button or the power+volume down?
Can you get to the bootloader from this point with volume down+power.
Have you tried to use a program that will flash the stock ROM?
Edit:
You can download a program called ODIN to download the stock ROM and it should flash it.
Also is the GS3 detected by your PC in this state.
Why would you use kingo root in the first place? Kingo root records your imei when you root.
Friend did know what he was doing and he didn't ask me for one reason or another...