Here's the obvious thing that both sides are missing. No where in the article does it mention how the child was reared, or if there have been outside influences.
Think about it. No baby has ever thought to his or herself "I think I'll become a sociopath, it sounds pretty rad". Unless some of the wires are crossed upstairs or certain areas of the brain are underdeveloped, babies are usually born with a clean slate and a level playing field. It's how a baby is nurtured that typically shapes development.
Now, the problem with this boy could come down to a developmental or personality disorder, or it falls squarely on his upbringing. If you read the article, it says that so far, all tests for conditions and abnormalities came back negative. Looks to me like it's an issue with upbringing.
At the top of the chain here are the parents. They are the ones responsible for shaping a child, and every action and inaction counts. You can be what you feel is the nicest parent in the world, but it doesn't mean squat if the child rarely ever sees you. Additionally, parents usually speak in extremes about their children. They are either precious angels that get straight As, are involved in every club and generally do no wrong, or they are a miserable sack of crap (just like their dad/mom) who'll never amount to anything, and unless the parent is flat out abusive and never wanted the child in the first place, it's almost always going to be the former. Therefore, you have to weigh what the parents say about their child against what they aren't saying, even if they're in denial or oblivious. The proof of the boy's actions is out there with plenty of eye witnesses, so there's possibly something going on at home that isn't being noted.
Outside influences are a real factor too, especially when kids are that young. The parents' other relatives and friends and how they all interact with each other may have an influence, the places the boy was taken to could shape a certain perspective, and while TV's used as a scapegoat more often than not, it can't be discounted entirely. Maybe the parents let him watch programming that isn't intended for him to see. Maybe he finds it himself when they aren't home. Who really knows?
I think this goes way beyond "oh, but he's just a kid" or "kids are monsters". Those are just surface reactions based on personal experiences, or the lack thereof. It doesn't really say or add anything to the topic at hand, though.
The mother has some really rosy cheeks. Beyond rosacea, I never knew that was a thing. :D