Reminds me of my son when he played in high school. His car was parked down the left field line in the parking lot. He was at bat and hit a log foul ball that dented the roof of his own SUV. What are the chances? Especially when there were about 30 cars in that lot.
And your son's story reminds me of one of my own.
Never considered myself much of a hitter, but one time, back in the '70s, playing softball on a concrete softball field, hit a strong line drive that just cleared the high fence along the left field line. The 6-inch or so wide softball struck the sloped rear window of a parked 1970's car, ricocheted off it hard and broke the large front window of a house roughly 20-feet to the left of the car!