Were the Engineers (Nephilim) on LV-223 attacked by Watchers that kept their first estate?

Ingeniero
MemberPraetorianMarch 02, 2017“From the Engineers' perspective, so long as humans retained that notion of self-sacrifice as central, we weren't entirely beyond redemption. But we went and screwed it all up, and the film hints at when, if not why: the Engineers at the base died two thousand years ago.
That suggests that the event that turned them against us and led to the huge piles of dead Engineers lying about was one and the same event.
We did something very, very bad, and somehow the consequences of that dreadful act accompanied the Engineers back to LV-223 and massacred them. If you have uneasy suspicions about what 'a bad thing approximately 2,000 years ago' might be, then let me reassure you that you are right.”
Movies.com interview with Ridley Scott regarding Prometheus (2012)
Vigilent Citizen covered the Prometheus, Watcher, Nephilim connection in the below article:
BigDave covered this connection in the cloak analysis from Chris in the comments.
Dr. Shaw's notes
Dr. Shaw’s notes equate the statues, archeological temple ruin sites, local history and legend to the Watcher descendent Nephilim builders (giants) of Earth’s early civilization.
Did Watchers that kept their first estate (see The Book of Enoch and the poem Paradise Lost) attack the Engineers (Nephilim) of LV-223 with a deacon alien(s) around 2000 years ago?
It appears that someone did due to the scream that was heard at the beginning of the Engineer holographic playback David initiated at the wall panel when the group from Prometheus arrived at the pyramid.
Thank you Chris for pointing this attack out in the summer of 2012, http://www.scified.com/topic/20052&page=4.