Other mistake: When Keene is hanging from the pipe in the shaft, he falls from it, and in the first second we see him falling naturally, in a 'standing' position. The camera angle changes, and he is now falling in a 'lying down' position. As well, when he hits the bottom (the nuclear cooling water), he doesn't splash further than a foot or so into the water. Falling from about 100 feet, he'd certainly splash down deeper than that.
Other mistake: When the team is in the grocery store, they rewind the security videotape (they play it backwards). They stop it at the last activity, when a man comes in and chainsaws his own head off. The body (and head) have gone blue/purple, and since everyone else died the previous night, we can assume that he cut his head off around 12 hours ago. At high speed reverse play, the time they spent rewinding would be only around 10 or 15 minutes of recorded time.