I'm at my wits end

My son attends DDI from 9-1 5 days a week. He is 3. We have an IEP. He has been at DDI since December. To speak to any of the teachers that see him he is an absolute angel. Never does anything wrong, mellow, follows directions, etc. At home he is completely different. Never listens tantrums on a regular basis, he's a runner so we are constantly chasing him
It's a fight to get anything done.
For about the last 2 months he has been hitting/pushing. I tried keep your hands on your own body. He knows it, he tells me and then hits again. I've tried time out. He wants to go in time out. I've tried asking if he likes being hit. He threw a tantrum because I wouldn't hit him. When we went to his CPSE meeting they looked at his behavior there and the reports and weren't sure the reports were about the same child. The reports did not match what they saw in 45 minutes at all.
Tonight was back to school night. I spoke to the teacher briefly about my concerns. Once again she was completely shocked to hear these things about my son. I told her this is why I don't come to school often because he is so different when I am around. She told me I should come because if they see the behavior they can help develop techniques for dealing with it. Today he kicked his cousin in the face because he wouldn't give up his blanket. I'm afraid that his aunt who watches him after school won't anymore because it puts her kids in danger. When I spoke to him about the behavior, he was punching me
The other day he came out of his playroom with a wooden toy hammer and started hitting the dog with it and laughing.
I don't know what to do. I don't know where to go for help. What do you when the people who are there to help don't believe there is a problem.
Sorry this is so long and for typos. I'm on my phine.

I'm at my wits end

Ask for home hours and parent training. Video your child while he's doing these things and bring it to your next meeting. Tell them his is regressing at home and you need to bridge the transition from school to home.

Re: I'm at my wits end

We went through similar with DS it was bad.

Fortunately (and I know this doesn't help now!), he has grown out of a lot of it.

He still has his moments but we also know his triggers.

We've also been very proactive about getting him seen early through Cohen's where some would say to wait until at least 7 or 8.

Many of my son's issues also come up when he is tired and unable to calm himself down.

His Dev Ped recommended giving him melatonin and the difference from this alone has been nothing short of a miracle.