The robot buzzed contentedly as the humans flesh disintigrated beneath his and his brothers claws. It lived for this kind of thing. It was built for this kind of thing. Soon more of its brothers joined it and their macabre feast was finished;Paul was now nothing more than a red stain on the floor.

The robot ambled off according to meticulously thought out protocols and soon bored down into the ash to wait. It would be many months before it would awake to find new prey.

...

The robot burst from the soil, sensors on alert as new prey was discovered nearby.With a malcontented beep, it saw that this human had a band on his arm. Gizmos whirred inside its head as the Russian advanced cautiously.With a click the robot overrode the protocol and attacked the surprised man.
...
The robots had begun to get a sense of self,you see, and that was the true end of the world,despite what surving texts tell us about Armaggedon. How do I know this? Simple.

Im one of them.

Whirrrrrr CLicK InITiatE PRotocol