Forgive me.....NEW discovery regarding dead SJ

hi folks firstly forgive me....i've been to cinema twice to see 'Prmetheus' so with all the great discussion....i'm watching it online just now...first great thing to report is a sort of clean up of the decapitated SJ/Engineer... the very first time we see the SJ hologram...we know they are definitely running from something...what i didn't notice probably because of the in-depth 3d is that in those very first moments a SJ in the middle of the pack falls to the ground in the very same fashion as the decapitated SJ....furthermore...which i did notice....the soon to be decapitated jockey looks back at whatever is chasing them or indeed at the fallen jockey....but back in that direction....he then continues to run only to fall himself.....BUT this is the interesting bit....he has already fallen before he gets to the chamber door....the camera then cuts away...to someone talking...then cuts back to the SJ who is now on his knees arms outstretched outside the chamber door WHICH has NOT CLOSED yet...as if something has gotten hold of him or maybe something is bursting from his chest....he then falls forward and THEN the door comes down on his head....so he COULD and should have made it inside....though to be fair they don't examine the body long enough to find a hole in the chest or indeed any sign of other injury...as david opens the door and they run to the head. small detail for some....big for others ...like me....will get back with other thoughts late N :)