jan and gary tyrrell's modest home was filled with valuable items.first glance, nothing appeared to have been taken. an early supposition was their killer was likely someone close to them. and no one was closer than daughter jessica. >> she is the person who could benefit here from this crime in terms of getting money. >> she had the most to gain. she's the only child and -- who had -- from parents that are very well to do with a lot that's gonna be left to her. >> so, she's gonna be questioned hard. >> yes. >> reporter: so that night, detectives asked jessica and fiancee jason down to the station to answer a few questions. the cops didn't let on they were talking to them not just as grieving relatives. but also as potential suspects. >> i'm obviously going to take a few notes, obviously, as we're talking. so don't let that, uh, don't let that bother you. >> reporter: the interviewer withheld details about the crime scene. a standard investigative tactic to see if a subject knows more than they should. he even threw out a theory that wasn't true - mu

gary's coin business. he'd started dabbling in it as well. he told detectives details that suggested a fellow collector could have targeted the tyrrells. >> he's got people all over the -- missouri that collect for him, and i know he goes to hotels, and meets people and he's -- he runs ads in the paper. >> reporter: according to mark, gary set up one of those meetings around the time of his death, and it involved a lot of money. >> he was actually going to sell $50,000 of gold for cash. it was -- it was actually a buyer who was going to give him that's all i know. >> reporter: he also mentioned text messages he'd seen on gary's phone from some other guy. >> gary asked me to read him some of his text messages and there were five in a row from some guy that he had taught in a class that was asking for money. >> okay. >> and i have no idea -- >> you don't remember? was there a name attached with the text? was it just from a number? >> i can't remember. >> reporter: and remember, gary was shot as well as beaten. could it have been with one of his own guns? >> gary has guns everywhere. gary has guns in -- in every drawer of the house i think. i mea