Just waiting for a bus - at the opposite stop a group who appeared to be mum of 2 DSs (I'd say aged 7 and 9 or thereabouts) and either her older sister or mum, not sure which.
Boys were being a bit boisterous/rowdy and start playfighting - the two women were sort of watching but also chatting, when the elder and quite a bit bigger boy hits younger boy round the head and shoves him agaist the wall of the bus shelter, and takes a toy he was playing with.
Mum then comforts younger child who is crying whilst older lady chases other boy down the road and ends up wrestling with him, with him kicking her, to get toy back. Toy is restored to other boy, elder takes it again, with force. Is given back, and taken again. At that point my bus came so I didn't see any more but all the time both women are laughing like its hilarious, as is older boy 
I was stood there with my mouth open.
I am not usually judgy. I shout at my DSs a LOT (mine are older tbf) and I have smacked in the past. I am not the perfect parent by miles. But there was something really quite depressing about this.
I did think about saying something but I'd have had to shout as they were over the road. Plus what could I say? You're a pair of idiots was about all I could think at the time.