Another attempt....

I have some serious questions about that whole thing. A woman saw him "assembling" his long gun in an unused room where bar carts were stored. Why was that room unlocked? Why did that woman not go immediately and tell the Secret Service there was a man with a gun in that room? Why did the Secret Service man at the table step out of the guy's way as he ran through the entry instead of trying to stop him?

Way too many loose ends in that situation.