Ive witnessed parents of toddlers/infant school aged children shout at 8/9/10 yo in a park before because they are using equipment their child wants.
On one occasion I'd met parents and their children, ours were all 8-11yo. We were sat on grass outside gated park and could see children.
The group of 8 children all went over to the 2 swings. They were turn taking nicely and even getting my Ds (who has asd) to turn take. A lady went over and told them to stop hogging swing. The 11yo said they weren't, they were just having a go each then they'd move on. She spent the next 5 minutes going on and on at the top of her voice to her children about "how it would be their turn next and how some children aren't very good at sharing"
Our group then went to seesaw and were taking turns again. She did the same at seesaw after using swing for about 2 minutes.
Up until this point I'd told out friends we should watch but let the kids have a go at dealing with it themselves to prepare them for going alone.
The woman clearly didn't realise the kids had an adult present.
She then went up to the 11yo and told her that her and her mates and siblings should all "fuck off home as no one could play in the park as they were taking over the equipment" 
I did go over at this point and point out that 8 children were managing to share 1 piece of equipment perfectly well and it was her and her children who clearly couldn't share so perhaps they should go home and come back when it was empty.
So yes, it's perfectly likely that the 9yos were doing something silly or hogging the swing. But it's also perfectly likely if it's never happened before and the Ds was upset by it they aren't misbehaved, don't get told off because there's no need and this woman was out of order.
When I was a kid if someone got on a swing and then we asked for a go we got told "not right now, X is having a go"
We are a far more patient generation!