My son was 18 when a similar thing happened, I can understand how helpless you feel just like i did.
It was a time of reflection for me as well, how fragile our lives are and how easily somebody who seems full of energy and life can be taken away.
It is a cruel world that takes your children and on this occasion we have both avoided it, some people are not so lucky
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I now look back on this period of our lives as a time of appreciation of what we have, I hope it is the same for you and yours in the coming months/years