Keep records of every communication with this person, all emails, phone records, etc Have an urgent meeting and discuss your concerns. Make it clear their abuse is not appropriate and will not be tolerated. Tell them you will have no option but to discontinue the project if they continue.
We are collecting all the videos and text abusive communications now. Have a ton of them now. We are looking for a way to strongly communicate to the client that we will not be tolerating this. We prepared an email but that that seems trivial compared to what he has done through his text and video communications.
Put the spotlight directly on them and reveal the behaviour unambiguously - video call, not email.