Securing an outdoor event like the one where Kirk was assassinated is among the most difficult challenges in the field. Much has been made of the fact that only six uniformed officers and a few plainclothes officers were at the Utah Valley University event the day Charlie Kirk was fatally shot while speaking to a crowd on campus. But in truth, doubling or even tripling that number would not have made a difference. Ticket checks and metal detectors can screen attendees in the immediate area, but they cannot defend against a sniper on a rooftop 175 yards away. Preventing that...