Who agrees there may be more than one Nexus?

I noticed in the Dead Space 3 Demo I saw the Nexus about halfway through. I noticed it was frozen, and may have been frozen for a long time. I made it to the end of the demo and saw it was alive, and trying to eat me. I was confused on how it got that way when only a few minutes ago it was frozen. Then my friend Jskillx wanted to play the co-op demo. When it started I heard the Nexus yell as I left the crashed ship. So first I hear it yell. Then I see it frozen in large amounts of ice. Finally I see it try to kill me. Please help.