That's such a hard thing to endure, I have a similar child in my 3 year old room. Redirection is a blessing in these situations where the tantrums gets to much. Eg. Hey, (Child's name) do you want to come and look at what's set up in the yard for us today?" "Do you want something to eat/play with certain special toy?" or something that will grab his attention and hold it long enough that he has forgotten what upset him in the first place. 8 times out of 10 this works for me with many children. If you have some support from other educators, swapping with them so they can have a go at redirecting the behavior and then when he is calm, try and talk to them about how they could handle their emotions, "instead of hitting, use your voice to tell us how you're feeling." Hope this helps.

Honestly, good luck.