The rifle used to kill Charlie Kirk has allegedly been recovered, authorities announced Thursday, and chilling messages allegedly inscribed on some of its ammunition are giving investigators a clue about what may have motivated the shooter. Internal communications by the U.S. Department of Alcohol, Tobacco, and Firearms appear to reveal notes taken by officials who immediately responded to the killing of Kirk, 31, on the campus of Utah Valley University near Salt Lake City. Within hours, they reported discovering the long-barreled hunting rifle, which was fired “from an elevated position on a rooftop in an adjacent building on the campus.”...