It probably wasn't Kingo (I've used it a few dozen times, and it's probably been used a million times). It's probably either something you did after you were rooted (you can destroy the hardware in the phone if you know what you;re doing, and can obtain root) or the phone just chose that time to experience a hardware failure. (I had an S3 working perfectly for months, rooted it and, within half an hour the motherboard decided to die.)
Under warranty? Boot into recovery (Volume up, Home, Power, until you see the tiny blue lettering in the upper right corner). Factory reset. Bring into the carrier and play dumb. "I was just looking something up on Google and Google kept closing. I turned the phone off, turn it on and ... well, this is all that happens, over and over."
If they can, they'll reflash the phone (it depends on the carrier and how they have their shops set up).
Not under warranty? I don't have a Rush so I don't know the exact procedure for reflashing it, but if someone has the files somewhere you can download them, downloading the files will be the most difficult part of the whole process. (Unless you consider dying of boredom watching a computer screen do almost nothing difficult.)
