I think it
was kind of obvious why he attacked them though.
You don't learn why the engineers changed their minds about us, humanity, but I think it's pretty obvious that he killed Weyland and the crew..erm...because we know they changed their mind about us, humanity.
People keep saying he "randomly went hulk on them"...but I don't think it was random.
They were coming to Earth two thousand years ago. Planet is a bioweapon outpost. David: To create, one must first destroy.
Shaw: Why do you hate us?! Why did you change your mind about us?! What did we do wrong?!
Those aren't theories that I'm making...that's what they actually say in the film.
We DON'T know why they changed their minds about humanity. We DON'T know why they decided to destroy humanity. I think that might be the focus for a sequel.
But, we know that they did indeed change their minds. Which should explain why he killed Weyland and the rest of the crew in the room.
Maybe I have some mental illness and was hallucinating while watching the movie, but I found all of this to be very obvious and don't understand why everyone else doesn't.