I had a little mindee who did this.
First of all you can put up with this but why should you!
I had to remove the little one from the room and give time out. I had to speak in a very firm voice. You perhaps could say "Not nice"
I had to get the parents support as I felt I was the only one being firm with the child.
The parents also need to set firm boundries themselves.
Now the little one is no longer being aggressive. Be firm be consistant!!
What would happen if the other fought back, the little could get hurt. WHy should the others have to put up with this unacceptable behaviour.
You can only control what happens at your home. The parents have to deal with this issue at home.
Is he doing this at nursery?
Do a log and let the parents know whats happening at every stage.
My littl mindee is a change person. I was not putting up with naughty behaviour whilst she was in my house.
Also be careful as your own child may start copying this.
All the best ....