cathy torrez." >> reporter: it was a shot in the dark. a tactic he'd picked up at a seminar for cultivating informants. >> and the patrol officer that is next to me starts kind of kicking my foot. and he's got an explorer scout who's riding with him -- a young hispanic female. and i look at her name tag and it was "d. torrez." turned out it was debbie torrez, cathy's youngest sister. >> reporter: who just heard you ask that question. >> correct. >> reporter: you had no idea it was her? >> i had no idea. >> reporter: debbie torrez -- cathy's baby sister -- was now 14 years old. eager, her mom says, to assist police because of everything her family had been through. >> she remembered that when we needed help, people came to help us. so she thought it was her turn to help others. >> reporter: which is why debbie was in the park that afternoon, and how she heard daron mention cathy's case. that is a weird coincidence. >> we don't believe in coincidences.