Been there too,
It is a shock indeed, and am 31 -
What I would do is to ask a child therapist what to do in this case, you are already seeing signs of distress. You are a great mom for noticing these changes in his conduct.
Even if we know death is part of life it is a huge impact to actually see it happen and even more so when it is unexpected and in a "normal" setting, not in a hospital. Even in a hospital, it is a shock, even if it is a stranger.
((Hugs))
PS About AH, please don't expect any magic.