If my mother's husband died before their divorce was finalized, who gets his money and accounts?

You see, my mom's hubby died recently this last week. They were going through a nasty divorce. Her hubby lied about his finances, kept on going to the hospital etc. He did anything to keep from paying support. Well sadly he did pass away last week. The day he died his niece showed up to collect his personal effects and so forth. Now his niece has control over all the assets/money. Is this really legal? I don't think he had a will. Plus my mother was still legally married when he passed away! So how could he give stuff away? What does my mother get out of this mess if his niece took everything of value! leaving only empty bank accounts.