I saw this show as well, however it was a rerun and wasn't a documentary and was on Exhibit A: Secrets of Forensic Science. It said that this was a guy who used to go to college and stay in his room all day (literally) and play a computer game called Morph. It said he used to call his parents for money and one day they stopped giving it to him. So he came home for a weekend and was playing Morph and he was getting really stressed out brecause it kept crashing or he couldn't pass a certain part (I can't remember). He then was filled with rage and killed his family with an ax but he killed his little sister by injecting her with drugs. The show did say that he probably came home with the intentions to kill his family anyway, so it probably was not the game, he was going to do it anyway, but the game stressed him out big time and he did it.
Also, if you feel the need to kill someone after playing a game you probably shouldn't be allowed outside and should be an institution or something. These people are already disturbed, the game didn't make them kill.
Oh yeah, he was supposed to be quite intelligent. And he had the nickname "Stinky Ahmad" or something from his friends because of his B.O.