after all, michael shot sam not once but four times. one of the shots was to the back of sam's head. >> reporter: so sam is laying here, and michael is right on top of him, basically, giving him the final shot? >> he would have had to have been. that's what the evidence indicates. >> one shot might have been an accident. not the three or four shots that he actually fired. that was no accident at all. >> reporter: but detectives wanted to know, if this wasn't an accident, why then did michael shoot sam? >> you had all these pieces to the puzzle and you tried to fit them all together. >> reporter: that's when michael revealed something that would turn the case on its head. he told detectives about an affair, but it wasn't the affair between sam and dianne. it was an affair he was having with the victim's wife, danielle dreher. >> they had been having an affair for four years. >> reporter: it was a mind-spinning moment. detectives had just discovered the victim, sam, had been cheating on his wife, danielle. now they were learning danielle had also been cheating on sam. >> everybody here is involved with somebody else. it was interesting to say the least.