Not easy and you are obviously doing your best with removing him.
Years ago I attended a toddler group and there was a child like this and the mum picked him up immediately and told him firmly "No hitting" and tied him into his buggy. He screamed blue murder and she and we just totally ignored him.
It took a few weeks but he got the message quickly enough.
She let him sit there for a good 15 minutes after he calmed down.
He was safe in the buggy and so were other children.
Some children hit. When parents ignore it, is when it pisses off other parents.
Firm, decisive action can help.
Also before you go somewhere, keep saying, no hitting.
He needs to get used to hearing that.
Hopefully it will pass soon.
It certainly will pass quicker with firm action.
Good luck!