When I heard the pops it sounded like a smaller caliber, a pistol round, but a .223 is also a smaller round. I haven't seen yet if they stated what the caliber was.
Security did fail if he was within 100-300 yards of a podium with a clear shot on the speaker, those snipers are on duty for a reason. A sniper should have likely already been on that roof if theres a shot from that vantage point.
When you push rhetoric like we've seen against him for 8 years now, people on the fringe, mentally stable or not, get it in their heads they need to act out this way. Happens on both sides. This is on the Dem Party and the Media in my book.