I'm not a gun guy and I've been lazy (I only read the very short article) but to me it seems like a 10/10 "What the fuck were they thinking?" screw up by the Secret Service.
Sniper shot at former President Donald Trump from 130 yards away on roof of manufacturing plant
If it was windy, it's pretty easy to miscalculate a shot.
I want to start a new grift for paranoid politicians: renting out huge portable fans to them that run at quickly changing speed/duration intervals, and claim it interferes with would-be snipers.