If you go thru the video, second by second, you will find that this goon had both training \and\ range time.
He was taught to quickly acquire a target field and shoot.
IT WAS A HEAD SHOT !
I’m watching a witness saying he and others outside the rally were shouting to law enforcement for minutes before the shooting, about a guy with a rifle on the roof of a nearby barn they were pointing at and screaming about. (Newsmax)