Lawfirm called adn wants husband to sign over custody of a child we dont know about?

We jsut got a phone call at 5 pm, from "the lawfirm of richard m lewis llc". Telling my husband that he has a kid out there, and the mother ped away and they want him to sign over custody. My husband hung up in shock before asking any questions. it could be possible he does have a kid out there. The firm is from jackson, ohio. we live in wapak. i tried calling back after he settled down but by thenit was after office hours. what should i do. and does this sound like a real deal here? we looked up the lawfirm they have a website, they are listed in the yellow pages, and on the bbb website. i hope you can answer my questions. also if it does turn out to be a real deal, can we recieve custody?