Can I be sued for this?

My mother's ex husband bought her a diamond ring a few months ago. My mother recently passed away and he is demanding the ring back. She did not have a will but I am beneficiary of her life insurance, was power of attorney for her, and I have paid her bills, taken care of her affairs, and packed up her apt. The ring was amongst her possessions and he has threatened physical harm to me and threatened to take me to court. Can he sue me for this ring?