they began to look into that, they found that the gun had been purchased by a young man named whitney knickerbocker. >> newly purchased. >> newly purchased. >> by a new name all together here. >> right. >> it had taken place february 2015, the same day charlie left cornell. the store had surveillance video of charlie's friend and fellow fraternity brother buying the shotgun, video that was shown to the jury. the frat brother was never accused of having anything to do with the killing.charlie had apparently convinced him to help buy a gun. >> friends say that whitney was told by charlie that he was going to go on a hunting trip so he asked whitney to help him. >> of course the prosecution says there was no hunting trip, charlie was planning a murder. in fact, before he got the friend to buy the weapon, surveillance footage showed just how intent he was on getting one. hours earlier, there's charlie. >> charlie's on video going into the walmart, attempting to purchase the shotgun. he is unable to. >> why is he turned down? why can't he buy the shotgun? >> he's a canadian citizen. >> which would requi