sounds like night terror/sleep walking
my little brother had that when he was younger... freaky shit.
when we didn't know what the fuck it was... my sister and i were in the living room... then my little brother (around 8 at the time) came running down the stairs with a look of pure fear in his eyes and he grabbed my shirt and pulled me towards him and yelled "they're coming for us!!! we're all gonna die!!!!" then he walked around really fast in a circle looking like he was holding the weight of the world on his shoulders... then he just sat next to me watching tv like nothing ever happened... then went up without saying a word and went to bed...
next morning when he woke up i said "WHAT THE HELL MAN!!!!!?
? WHO WAS AFTER YOU!!!? YOU WERE ALL CRAZY!!!" and he said "what? what you talking about?"... he didn't remember a thing.
kept going on for 8 years til he was 16 then it just went away...
we got so used to it that sometime he'd come down yelling about how the house is burning and the fire will eat us all up and we'd just say "sit your ass down and have a sandwich, we're watching tv"... LOL