He was found on some abandoned underground ruins by some miners on an expedition, it was sitting next to a minecart full of diamonds, emeralds and gold.
The miners without thinking just took the minecart and sent it to the town, but the rails had a detector rail and a piston activated somewhere.
They thought that it was a trap somewhere so they just ran away, but they didnt knew that a redstone ore block was pushed below the robot.
The Robot got activated and it scanned the area, but he didnt saw any minecart full of treasure. He started tracking the minecart and found the town.
It went savage and started destroying every single house searching the Treasure.
The guards of the town were unable to do any kind of damage be cause it was made of full reinforced iron blocks.
Then after destroying and killing everyone in his path found the mayor. They stared at each other without any word, the wind was the only thing heard, it was such a tense moment. The last battle started with 1 word wich was:
"Exterminate"
They charged to each other and after that.
No one lived to tell the story...
-Abandoned Miner.