Scary. I don't have nightmares often (or at least I don't remember them) but when I do they're really visceral like the one you describe and I always have to do something to confirm that it's only a dream. What I really hate is when I'm having a nightmare and then dream that I wake up so I can prove it's not real, but actually I'm still asleep and the nightmare seems even more real. Luckily that doesn't happen often.

Your nightmare made my chest constrict. That's how much I could feel it.