The local Social Services dept. will have an Adult Protective Services Unit to whom it should be reported. Like child neglect and abuse, it can be hard to document. The quality and professionalism of DSS staff may vary, or, if they are understaffed and overwhelmed, they may not follow up as carefully as is warranted.
It would be going above and beyond the call of duty and perhaps blow your relative's anonymity as the complaintent,, but if your relative has the opportunity to document anything (taping the verbal abuse, photographs of the trashed possessions), that would be helpful evidence of the complaint, and depending on the DSS unit, either support them or hold their feet to the fire.