If he wasn't armed, then he shouldn't have climbed the ladder, but immediately alerted authorities to what he had seen. There is no way the roof of that building should have been left without at least a spotter or two on the top of it. Extremely poor security procedures. You're not supposed to leave any option open to a shooter, but try to cover as many bases as possible to prevent what happened from happening. It's freaking unthinkable, and no one will ever convince me that it wasn't done on purpose.
Trump has held many rallies around the country for the past 8+ years, inside and out, with millions of people in total attending them all, and this occurs just a day before the Republican Convention begins in Milwaukee? And a "loner" is allowed to walk onto the grounds carrying a rifle, climb a building he knew had no law enforcement coverage on it, and shot the President, killed a rally attendee, and none of it was planned by someone other than the shooter? That's total BS. There are no such things as coincidences.
Maybe the loner hid there much earlier. You are supposed to have people on every “peak”