Continuity mistake: Before Alex and his friends enter the airport there is lady in white that crosses the door at least 3 times.
Continuity mistake: When you first see Carter's car you can see that is says "SS" on the front. Then when he almost hits Billy at the school it doesn't say it. Then when he is on the train tracks it says "SS" again.
Answer: The scene where Terry was killed was most likely shot during the day. It is quite common for film makers to film a scene during the day to get the right lighting effects and then later CGI the night sky and the proper shadowing. This is most effective when you have an area that would otherwise be too dark or have environment that wont allow for the proper lighting for a night shoot. As for the bus, your guess is as good as mine.