It went against everything the movie had said gets the aliens to attack. They can't sneak attack. They have to hear the thing before attacking.

The second part is the killing of the raccoon. It fell off the house and made noise which we're supposed to believe will bring the aliens. It doesn't. So the raccoon is quietly walking down a path and the alien does another sneak attack. Like retribution for making noise minutes earlier.

I live the movie and the sequel but those parts really bug me.