What are your rights if a child assaults you?

I don’t mean if it’s your child, I mean if you’re an adult and kid that’s maybe 10–13 is harassing/assaulting you, do you have a right to defend yourself even if they’re just a kid?

I found this video and the way the boy attacks his own mother, I wouldn’t doubt he would attack someone else who tried to confront him:

https://www.youtube.com/watch?v=3qS-FxDcVq4

And what causes a child to act like that anyway?
I remember being 8 or 9 and playing in a bouncy house with a little girl about the same age. Her brother who must have been around 12 came into the bouncy house and pushed me down and sat on top of me and yelled in my face and proceeded to grab me by my leg and drag me around the bouncy house until I started screaming and his sister convinced him to let me go. No adults came to help me even though I’m sure they heard. When I threatened the boy with telling an adult what he was doing he said he didn’t care.

I always wondered if he became a felon.

I’m still kind of disturbed by the feeling of screaming and needing help and people just looking on.