At soccer practice

I was in soccer practice and there were about 10 men (absolute strangers) sitting on the bleachers who we assumed to be players after our session. Someone then took a picture of us playing and our coach immediately came over to him and told him to delete it. It apparently happened twice and I find it VERY disturbing. We are teenagers. I had every urge to confront the men and question their behavior but I was told to calm down.