Ok, a couple quick thoughts:
This "unknown perpetrator" could be really important. I think we should discuss this.
Could EG have left Lucas home when she went to OG because she was meeting a male "friend" there?
I'm surprised at how many are saying that they don't think that JH was abusive towards Lucas or not as abusive in general. First of all, what is "more abusive"? More often? More severe? Does it matter? Secondly, everything we have heard about JH from the police reports of the domestic violence with EG, to EG's kids saying he "uses loud voices" and "bad words", him getting defensive when family members talked about it, his nonchalance about it on the news... everything shows us that JH is abusive. I'm not sure why so many think he didn't abuse Lucas, too. Of course we don't KNOW that he did, but the chances that he did when he was abusive towards everyone else, are way higher than the chances that he wasn't.
And one more point that doesn't need to be discussed because it's a sensitive topic, but I think people should really reflect on: when we're talking about "how can we prevent this from happening?", I think one thing we can do as concerned members of society, is look at society's acceptance of using violence against children at ANY level. How much easier would it be to spot, and even for the children to recognize their own abuse, if we stopped drawing subjective lines about what is an acceptable level of violence and what isn't? Again, I'm not trying to start a debate, it's just food for thought.