Neighborhood kid is targeting my daughter and I need help to make it stop.

My daughter is six and has just started to go outside alone. The neighborhood kid is 10. My daughter plays outside with his sister and some other children, and it has been going really well. However, this kid has multiple times now pushed her so hard she falls hard down. I have talked to his mum about it, and she said she talked to him about it and she cant do anymore than that.I am honestly very unsure on how to handle this. I don't want her to feel unsafe outside, and I have told her its okay to come in when he comes and isnt kind. Am I overreacting in thinking that the kid is old enough to not do it? His sister and the other kids tell me he does it without provocation and his mum tells me he struggles with impulse control. I am afraid it eventually will escalate to a bullying or that she gets seriously hurt. I am also anxious bc I don't want her to be afraid to be outside playing with her friends! He does not behave like this with the other kids but they are older and bigger than mine daughter.Do anyone here have any experience they want to share? Any suggestions? via /r/Parenting https://ift.tt/3ckbGKJ