emma. he had nothing to do the shooting. but, he did have his grandpa's gun. >> they're gonna find a way to put this on me if they find the gun. can you help me get rid of this? >> the boys were willing to come for riley, but not help get rid of evidence in a murder investigation. instead, they called lieutenant merit. it's amazing that they called. >> absolutely. >> this is a big piece of the puzzle. >> absolutely. they could very well mind their own business. >> riley told his friends that he plans to go to the bluffs, high above the tennessee river, and toss the gun into the water. police hatched a plan, a bold and risky sting operation. have alex and noah go with riley, and the moment they see the gun, signal detectives who would swoop in and make an arrest. this potentially could be very dangerous. >> absolutely. you have two boys in a car with a guy that's believed to have already killed somebody with a murder weapon, this is a