Need advice pls. We were in the park with my parents and ds and dd were squabbling. Ds kicked dd (she was also kicking, they are 6 & 7). DH wasn't with us, he was at home. I was sorting it out and my Dad overheard and came up. He saw ds kick dd and grabbed his arm, saying' If you kick someone, someone else will kick you back harder'. Ds then laughed. So my Dad said to him again, 'If I kick you it'll really hurt.' Then Ds again laughed. My Dad had started to walk away but overheard and then flew at my son, knocking him to the ground with his shoulder. I said, too late, 'Don't push him over!'. My Dad went off and my son was ok, just looked a bit shocked. My parents later went home and now I don't know how to say to my Dad that this behaviour is not on. I am so upset. My son seems fine but I don't want it to happen again. It has happened once before, when ds was about 3 and squabbling with dd again. Dh, again wasn't there. My Dad grabbed ds roughly by the arm and I, again, said not to do it but he doesn't ever say sorry or that he shouldn't have done it. My Mum just doesn't say anything. We've only just started to communicate better and things were going well but now this has happened. I just don't want to see my parents now which isn't going to help rectify the situation. Any advice would be welcome.