detectives mcdonald and szalbirak immediately brought him down to the sheriff's office for questioningught, but he's willing to talk to us. and we were very much ready to listen to him. >> reporter: michael outlined for detectives the details of the shooting. he started by insisting it was all an accident. >> i never intended to pull that trigger. >> reporter: but detectives weren't so sure. after all, michael shot sam not once but four times. one of the shots was to the back of sam's head. 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

she's got to have something to do with it. >> reporter: and as mcdonald and szalbirak sifted throughecame more confident they were on the right track. what they discovered stunned even these two seasoned investigators. for over a month danielle had been spying on both sam and dianne. >> danielle was just totally obsessed with what sam was anything that i've seen before in investigations. >> reporter: what's more, it appeared to them that danielle had persuaded michael to help her. >> they had basically stalked them. >> they actually put a tracker on their vehicles. >> reporter: this is spy equipment? >> correct. >> reporter: sheriffs deputies discovered it in the wheel well of sam's pickup. police also found evidence that both danielle and michael were taking surveillance photos of sam and dianne. this is a photo taken of them on sam's boat. in this one, they're on dianne's balcony. >> michael would have been somewhere across the lake there. and that's where he would have been hiding in the bushes. >> reporter: it seems like a perfect spot, actually, if you wanted to spy on someone.