Welcome to typical childhood after a long day at school. This is what kids do. They "keep it together" all day at school, and "let loose" anything pent up when they are in their "safe" space among safe people that they know and trust. Consider it a compliment of sorts. Your son trusts that you will still love him, even when he is a brat.
Word to the wise: Take FOOD with you. Or send some for your kid to have on the bus or immediately after (on the walk home). Food makes all the difference for some kids... For some kids it's more just being alone or blowing off energy outside or in the quiet of their room for 30 minutes after school.
When I would pick up my kids after school I ALWAYS took them something to eat. A pack of peanut butter crackers, or grapes, or a granola bar... something I knew they would eat without complaint. They would be SO atrociously unhappy and grumpy with me and each other that I practically made it a rule that they couldn't talk in the car until they'd had their snack. It was like a miracle took place after the food got in them.
It isn't the talking to him that changes his behavior... it's the food. And the comfort zone of being amongst "friends" instead of the combat zone of behaving at school under rigid rules.
ETA: Sorry, meant to exclude the hitting from being normal. It's not. It's totally unacceptable. Does he hit you other times? That's the most ginormous no-no of disrespect a child can do to a parent, in my opinion, at that age anyway. Just NO. I suspect, however, that you will see a reduction in it immediately if he is supplied with food before given the opportunity to act out towards you.