Continuity mistake: After the private starts shooting and the group Mark Wahlberg is in breaks into smaller groups and starts running in the field ahead of the wind, his group consisted of himself, his wife, the little girl, Jess, and two women. One woman was heavyset wearing blue with dark hair. The other was thin with red hair. The next scene of them running ahead of the wind, their group now has two boys, one black, Jerry (I think), one white, Josh (I think), instead of the two women. (00:48:28)
Revealing mistake: When the builders are committing suicide the guy in charge keeps turning earlier to the areas of the falling instead of after they land. A special FX and timing error I guess. (00:06:20)
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.