This isn't really a PTSD thing but I've had flashbacks before and they are way scary, and probably similar to what someone with PTSD would experience.

One time I made the mistake of attending a conference that was held at my old "alma mater" so to speak -- the college I was going to when the whole "storm" first broke out upon my life. I made the double mistake of staying in the dormitory where I'd been living when it all happened (it was summertime so they had dorm rooms available for conference attendees) and even though it wasn't the same room just being there in the building was enough. My anxiety levels went out the roof when the conference sessions were over for the day and I was all alone in that room ... I went out and got some alcohol to drink trying to chase the anxiety away ... another big mistake ... I ended up having so completely full blown a flashback to this day I have NO idea how I ended up where I did -- who found me, how they found me, or ANYTHING. I ended up (somehow) at this house where one of the conference presenters lived or was staying during the conference (can't remember which), shrieking and sobbing hysterically, babbling in another language (they told me it sounded like Gaelic to them; I don't know or speak Gaelic AT ALL, not even one word), and at one point locking myself in a bathroom there with a knife because I was going to c*mm*t su*c*de. I remember those few items but I have no idea how I got to that person's house nor who took me there. I think a couple of the ladies I'd met there at the conference -- a threesome of very nice & friendly gals my age from Florida who were attending -- found me in this "state" and got me there somehow but I don't remember anything after I started drinking. Some of that might have been the alcohol, true, but the majority of it was the severe state I was in due to the flashback. It started there in the room before I even started drinking, and I was drinking to try to chase it away but it only got worse. I thought it was 1983 again and I was reliving things like crazy. Oh man it was bad. Totally out of control.

The people were very kind to me and stayed with me, talking to me, comforting me, and trying to calm me down. Eventually I did come out of it. I heard them talking about calling the ER or ambulance or some such and I totally begged and begged them not to, I was so terrified of being locked up somewhere and so embarrassed about my episode and so scared of someone taking my kids away from me because of it (they were still small back then, were at home with their father while I was away), etc.