He kept running.  Even though his hands were shaking, even though his legs burned, even though his feet were numb, even though his skin was cut and bruised, even though his heart raced, he kept running.

He didn't know why.  Why everyone dropped to the floor, lifeless.  Maybe it was because they were standing still.  Maybe it was because they weren't running like he was.

So he kept running.

Soon, he found an abandoned building to rest at.  Thankfully, the water fountain still worked.  The water felt nice and cold against his skin.  It filled up his empty stomach.

After the refreshment, the boy leaned against the wall.  Catching his breath, he noticed something in the distance.  It was another human.

'That's weird,' he thought. 'I thought I killed them all.'

He stood up and rushed to the human at an incredible speed.  The human never saw it coming.

The boy walked away.  Yes, he could never figure out why humans dropped to the floor, lifeless, so easily.  Maybe, one day, he would.