 Politics must never be a literal battlefield, a God forbid, a killing field. 20-year-old shooter, still no known motive for the attack. ABC is reporting that a local police officer nearly stopped it, but he was forced back after the suspect turned the gun on him. NBC is reporting the roof where the shooter was perched was flagged as a potential trouble. Serious questions about the Secret Service in the aftermath of the event. Already Congress is vowing hearings.