All electrical went black on engine start

I have a 1998 GMC Sierra XLT, I drove it yesterday with no problems. I've had no indication of problems untill today.
I went to start the truck and everything was normal, all dash lights and fuel pump running, I turned the key to start and everything when black. Every system on the truck was dead. I opened the hood and the battery was making a soft buzzing sound. I disconnected the negative terminal and cleaned both. I then reattached it and the hood light came back on, so I tried to start the engine again, same thing, everything died and the buzzing started again. I took out each fuse and tried the battery again and it sparked every time. What could have shorted out to cause this?

check your battery cables to see if they are coroded. Also check your starter conection. But it sounds like the positive lead in between the two.

Even a new battery can die like that. They just short out internally. How old is the battery? Take it to Autozone and have it checked out.

It was the battery, 2 cells had shorted out.
The battery was only about 2 years old, had it installed by the dealership after the old one went dead over a weekend of no driving.
So I just assumed the battery was newer and ok.
The garage had already came and towed away the truck, I even had a spare battery in the basement. I could have saved the towing.
Any how I'm glad it was simple and not electrical system short.
Thanks for your help.

Also: charging a shorted battery ruins a battery charger:(
Mine just started smoking after about 1 minute, thats why I thought there was a short in the truck wiring, never thought to blame the battery.