Spoiler Alert hope this helps

Rating: 10/10 (7 June 2012)

Hi there, my interpretation was that the engineer at the beginning was sent to create life on earth, and remember that the ship may be a different shape but might not be a weapon ship but a transport ship. Now the chances are that humans were created to be hosts for the worms in the jars which would create aliens eventually as seen in the end, when a possible queen is born/evolved. So did the original xenomorphs create the engineers to create other hosts? well that is another debate altogether. now the engineer that is awakened by the crew was hostile because.
A.He had been asleep 2000 years in shock and a survivor of what killed the others.
B.Put there by the other engineers because he was evil , who had decided not use earth as a host planet.
C.Humans had become evolved way beyond what was expected and the arrival at the planet was a signal to use us as hosts and he was trying to wipe out the crew to stop them warning the earth about its impending doom.
D. He was planning to blow the planet up as he left the atmosphere so didn't
need to worry about the ship or other crew members.
E. He was annoyed that humans had created life in David, (as we do not know what David said it makes this hard to know for sure) but he could have said my maker is pleased to meet his maker. which could have caused the angry reaction.
Hope this helps or brings other answers.
Jason