mark. searching for his killer, but not coming up with easy answers. because he was so close to his friend an employee, we d.a. mclellandhe investigation. investigators had to do what they could. >> anything that anyone can think of there are going to do it. >> marks checks in his personal background don't go anywhere. so they looked in his professional cases, from 30 years ago, to a few weeks ago. >> how did you go from it could be this person? or this? person >> you see if they're locked out up, you see where they are, their whereabouts. there's usually something specific about someone's case that could give them cost to have a grudge. >> four weeks into the investigation, a tip came into the crime stoppers tip line which looked like a big break. >> the tipster said that they had been in a bar in a small town and kaufman and overheard to white men talking about the hasse killing and talking about how they did it. >> so they use the crime stopper system, the tipster remained anonymous, this was gonna be a game-changer. investigators would need more invent mission or luck. >> you're still looking for the big break or lu