Originally Posted by
Abra
Sounds more like a night terror than a hypnic jerk... "Pulling/moving down" seems slower than the sudden falling/tripping in a hypnic jerk. Also doesn't explain the screaming. Night terror explains the screaming, but the feeling doesn't match up (unless the pulling/moving was scary or made him feel uneasy). In night terror, people usually feel fear, anxiousness, or uneasiness, not really a movement...
Maybe it was hypnopompic SP. You were exiting a dream, consciously felt SP, continued sleeping ==> Night terror.
Just a guess. *shrugs*