need advice

Hi there

I have a 4 year old son who has asd (just recently diagnosed). He is very hyperactive and struggles with frustration. He roars all the time and where he doesn't understand personal space he does it right in your face. He is a very big 4 year old and his behaviour is scaring his little sister who is 2. He doesn't listen and doesn't understand that he scares her. Does anyone have any advice to try to calm this behaviour?