When the killer drives the car against the door, we see the main character attempt to open the door, and succeeds a few inches. Yet later, the room fills with water as if completely sealed, and no characters think to try the door.
Why did they park so far when the parking lot was empty?
A
They parked so far away because David was punishing Corey for making him stop at the ATM when he didn't want to. Parking so far away forced Corey to walk in the very cold weather.
That statement is sort of true but really it's just something the film makers added in to make it easier for the killer.