What I see is a train that was able to stop, thanks to the sharp eyes of its engine crew, at a potentially treacherous rock cut where a couple of young trespassers with questionable motives were no doubt observing operations in order to plan their forthcoming placement of explosives in order to bring down the sides of said rock cut into the path of that evening's crack passenger/mail express. Flag in hand confirms that they're anti-government extremist patriots, the very sort that would commit such acts. The special agents can't arrive on scene soon enough. It's Alcatraz for those two kids.