I think having him seen by the counselor is key. We had a similar domestic situation, and my 6 yo ds was diagnosed with PTSD. It's possible that your ds is also suffering from this, or some other condition related to what happened. PTSD can cause memory and learning impairments, but it can also be complicated by underlying learning disabilities. There are also other conditions that can cause this kind of behavior. A full-scale neuropsych evaluation can disentangle this. My son's anger has mostly been turned inward, but he spoke a lot about hurting himself, being bad or evil, growing up to be a bad guy or take drugs because he was bad, others hating him, etc. My ds has been in therapy, and has some classroom interventions to help him manage some of his issues (in school, impulsivity). We've seen progress in some areas, but there is some backsliding too, especially with some social problems he's having.
I don't know that it's necessary for you to keep him at home, but I think if you are able to be at home, and have the patience to help him work through these emotions, it might be best to do so for the time being. I don't think you're being overprotective. Once you have some answers, and a plan to address his needs, you can decide what setting is best for him.