Plot Hole: How did killer know the train was arriving?
Seems to suggest to me that the "people" paying Frank's character to assassinate the President were INSIDERS who wanted him taken out. How else would a 2-bit punk wannabe anti-hero know the whereabouts of the most powerful man of the planet? Just like the JFK conspiracies, many people to this day think it was an inside job. Some suggest CIA or even the FBI(J Edgar hated the Kennedy's). Some say Mafia(and you got to believe the mafia had paid connections in the White House).
So, how did he know the train with the President was coming and that it would stop in Suddenly?