I need to help my friend with his nightmares?

My friend has been having these gory, horribly vivid dreams the last couple nights and the last one made him wake up sweating, screaming and crying because it involved him being forced to watch the slow and brutal murder of his family, who is mos important to him. What is the interpretation of this dream? And now he's terrified to go back to sleep, are there any techniques to help him sleep better or without nightmares?