A traumatic event of this magnitude  could have a profound psychological impact on a person manifesting  in various forms such as flashbacks,  anxiety attacks, insomnia, nightmares , increased stress levels ,etc that can cause significant distress, interfere with the daily life and delay the  recovery from the trauma. As such, kindly get a detailed evaluation done by a Psychiatrist to find out the cause of insomnia  in your husband  and also for the  formulation  of a management  plan to take care of  his mental  well being  and help in his  recovery from the trauma.

If he has trouble sleeping. Getting a detailed evaluation by psychiatrist rule out anxiety/ depression is important. He can use medication accordingly.