Saw a player wasting all the robots

I was at the Whitespring on Saturday and some level 500+ player was systematically wiping out all the robots inside the mall area.

I came down the stairs from the refuge and heard gunfire. Dude was standing there just mowing down robots (not vendors, only "security").

What was the point of this? Is there a reason for it?

Edit: he was using different weapons so it was probably the killing robots with different weapons challenge. I forgot about it.