Terrible situation but nice that you are aware and that you suggested for him to turn to family. Needed in similar situation so and I understand it has become quite common or at least people have been more aware recently regarding trauma and cptsd (and the nightmares).

For those who have in their life people with emergencies due e.g. emotional flashbacks let me put this here: https://old.reddit.com/r/CPTSD/wiki/firstaidkit

What has helped: “From surviving to thriving” book, “The Dialectical Behavior Therapy Skills Workbook”, ipf protocol, avoid stoicism related thinking