suspicion fell quickly on marc's dad, jack despain. elle's mom heard about it when she called to tell a relative that marc was dead. >> somebody's murdered marc. and he was like, "oh my god." he said, "have they found jack despain?" >> reporter: he thought right away it was jack. >> uh-huh. >> reporter: because anyone close to jack and his family knew, a poison far more potent than money had come between father and son. >> i never saw it coming. i don't think marc ever saw it coming. >> reporter: it began, said michelle, when her 13-year-old daughter told them an ugly story, that her grandpa jack asked her to take nude photos of herself on his phone. marc called a family meeting. >> marc told his dad, there's a problem. we want to help you. you know, we're not here to point fingers at you or judge you. >> reporter: jack swore he did nothing wrong. marc called in the police. tana, jack's wife of more than 30 years, left him. moved in with marc and michelle. well, how do you prepare for a thing like that? >> you don't. you don't prepare -