If you are mowing your lawn and the mower hits a rock that breaks a window of a passing vehicle who is responsible for the damage?

If a person I hired is mowing my yard and the mower hits a rock that breaks a glass in my storm door is he liable?

If you were driving the car, who would you think is responsible? Your mower threw a rock that broke an innocent driver's windshield. Of course you are responsible! Be a man, accept that responsibility, and fix the car!