Hair pulling

Hi everyone. My Son is 6 years old, over the last couple of months he has started pulling everyone's hair, sometimes when he doesnt get his own, sometimes due to sensory over load bit also sometimes he does pull for no reason.

It is getting to the point where he literally pulling clumps of peoples hair out. He has such a tight grip that we can't get him to let go. Once he does let go we praise him that he let it go but how do we go about trying to get him to stop pulling hair.