What got Chris & Natalie?

After the guys return from the car lot, with the cables for the van and come back to the Yuri's van, where Chris and Natalie are; they see that the van is thrown upside down and Chris and Nat are gone and when they look at the recording of the camcorder, they see something getting Chris and Nat and throwing the van about, so it must have been something big and strong, not like those standard humanoid mutants, but they never show what it is but only Nat being lifted up by a tentactle or something.

What could this thing have been as they never show it again in the movie?