We are waiting for a further assessment for my 8yr old grandson.

My 8 yr old grandson is awaiting a further assessment to identify his future needs. He has global delay identified when he first began nursery. However , school, G.P. parents and myself are still awaiting for another assessment, where Autism has been mentioned by his senior teacher and head.

is there anyone out there that could explain to me some of his recent outbursts or meltdowns. Example for instance…… Today he would not let his little 2 yr old brother take home to their house a little toy. My 8 yr old was repeating “ no, Charlie can’t take it home, it must stay at Nanny’s” He was hurting his little brother and nothing or any words would pacify him. He became extremely upset and angry. I read up on something called a possession syndrome, but is it that. Or is it a sign of my 8 yr old being within the Autism spectrum? 
please I would be so appreciative if someone out there can recognise this behaviour, it has been happening very, very regular over the past year and I have never witnessed this type of behaviour from any of my 5 grown up children or any of my 10 grandchildren. It is so very upsetting to see him in such distress.