Character mistake: When Chris joins the Marine unit they are going to breach a door. Chris removes his shooting hand from his weapon to signal the breacher. He would have used his support hand.
Character mistake: While watching the events of 9/11, the broadcaster notes that the "south tower is collapsing" while footage of the North tower's later collapse is showing. The south tower fell first, 29 minutes prior to the north tower. (00:22:25)
Chosen answer: Chris has "shooter's strawberries" on his elbows, which are red callouses caused by lying in the sniper's position for long periods. He notices the same marks on the elbows of the father, and realizes that he too is a military sniper.
Sierra1