smaller younger child bullying an older bigger child

So I was at chick fil a today and a tiny little boy was totally picking on another kid. He wouldn't let the other boy into the play area, the other boy went to his table and sat down. the mother of the smaller boy saw what was going on and asked her son amd asked of he wanted to come out. no scolding no punishment. he runs off to play. the bigger child sees he's in the clear and goes in the play area. all the sudden out of no where the little boy comes out of no where pulling, pushing, and hitting the older boy. The boys don't know eachother, and the older boy looks traumatized. The mother of the little boy finally goes over after I give her you better go get your child look. again no scolding or anything. She asked him if he wanted to eat. I felt terrible for the other boy. his mom didn't say anything to the other mother. the one time my kid got pushed at the same playground I said something to the kid and the mother. what would you have done? oh and before you say maybe the smaller boy didn't know what he was doing, he did. he was fully aware.