Tyler Robinson was a patsy part 6 the time stamps dont match

Charlie Kirk was shot on a Wednesday, Tyler arrived to the university at 8:39am. The University would have been packed with student walking to class all over the campus. How did no one see him scouting the rooftops? How did he know Charlie would be setup in a location that he would give him a clear line of sight? He retrieved the gun at 12:15, made it to the prone position at 12:22, then took the shot at 12:33? Some how he also assembled his rifle and disassembled his rifle and that exact same period of time?