Notice the more intense and sharper border on the opposite side of the ring. More diffuse on the near part of the circle. I suspect that someone was standing on the opposite side and tried to kill a weed in the center. Is that a clump of Bermuda in the center? Can you find a dead weed in the center. Maybe they were using a hollow cone nozzle.
Do you have big dogs in Leonardtown? Is there any sign of intensified green?