Flashbacks are memories. Sometimes, survivors have a strong memory that seems very real to them, like they are actually re-living it. It can be so strong that they thing they are back in the place where it all happened. To them it can be so real that they see it, feel it, taste it and smell it. Often the memory repeats itself over and over again.
Other people can help the survivor by not panicking but just being there. There are many ways of keeping a survivor grounded in the present. Even if someone slips back into nightmare memories, you can help them pull out again. The main thing to remember is that they are not going crazy, they will not be damaged and will pull out of it eventually by themselves.
Ask the survivor, while not in flashback or panic, what the boundaries are with them. i.e. a hug or someone holding a hand might help some people, but is an intrusion if the survivor does not want or need it.
Talk and keep talking. Remind them they are safe. Remind them who you are and where you are. Try to get the survivor to breath slowly and deeply. Try to get focus and listening to you or other things that are around. i.e. radio, taped music, etc. If you can get the survivor to hear you, you can let them know that you weren’t there during the event. By listening to your voice, they can gradually pull away from the memory. Keep your voice quiet, gentle and steady. Keep using the survivors name as you are talking.
After the flashback encourage the survivor to talk about it. It may not be a good idea with some people to talk about it right away, but make an arrangement to talk about it soon. Some people do want and need to talk about it right away. Take your lead from the survivor in this. When talking about it, the flashback may come back. This is normal.