Factual error: Filbert is in the southwest corner of PA. It is very far out of the way of Harrisburg and completely off the route from Philadelphia to Harrisburg.
Factual error: There are no tracks, stations or train routes in Filbert, PA.
Factual error: The cars the train is pulling for the Philadelphia to Harrisburg route are not ones that represent any passenger cars used for the Amtrak or Keystone routes. They are SEPTA cars on an undisclosed route, other than the Harrisburg line.
Answer: It appears so. M. Night often uses the color red in his movies as a visual clue that something emotional or violent is about to take place. If there was blood on the swing, it could be a forewarning to the audience that the house in question is more dangerous to the main characters than originally assessed.