My 9 year old son went to his friend's house after school. The dad collected them both from school and took them to the park. When my son got home, he said that the dad went back home to get something and left both my son and his friend (both 9) alone for 10 minutes. In this time my son fell over and grazed his knee and said an old lady came over to him to see if he was OK. Son wasn't frightened, hurt or upset amd while he is quote mature for his age, I have never left him alone for any amount of time. I'm annoyed and am not sure if I'm being unreasonable. I feel like I can't trust the parents again. Am I mad? I can be a bit over protective but aibu in thinking you don't leave 9 year olds alone in the park? Or maybe it's OK. I don't know. What do you all think?