Well just a quick script:
Code:
function Update(self)
    for actor in MovableMan.Actors do
        local avgx = actor.Pos.X - self.Pos.X;
       local avgy = actor.Pos.Y - self.Pos.Y;
      local dist = math.sqrt(avgx ^ 2 + avgy ^ 2);
      if dist < 250 then
          self:GibThis()
      end
   end
end
Distance is changed, obviously