How do i make an over the shoulder 3d camera?

so im trying to make a fighting class script that uses a forced 3d camera. the way i want it to work is to always be looking at a certain part which would be defined in the script, but also be over the player's shoulder. the end result would look like this kinda https://i.imgur.com/6iGI5JA.gifv

but no matter what i try, i cannot figure it out. anyone know how i can do this?