1570 James Stewart, 1908 King Carlos I of Portugal, 1919 General Emiliano Zapata, 1963 John F. Kennedy, 1968 Martin Luther King Jr., 2003 Zoran Đinđić were all assassinated. Other than some coups these are the very few that were assassinated with rifles.
Yet this is the thing that terrifies security details. It is the thing that TV and movie plots are made of. The lone gunman in his perch taking that multi yard shot from outside the parameter and killing their principal.
A good sniper is almost impossible to spot prior to the shot and is often not seen after the shot. The gun barrel pushed out the window advertising the location should never happen. A real sniper knows that it is patience that is his strength.
This country is full of men and women that have rifles perfectly capable of taking a deer at 500 yards. There are people that are capable of long distance shooting where they hit targets at well over 500 yards. The M-16 with a 20 inch barrel is perfectly capable of putting rounds on a man size target at 500 yards with iron sights.
In 1966 some asshole climbed the University Texas clock tower with multiple rifles and started shooting at people. He shot for 96 minutes, killed 15 people and injured 31 people. Civilians and police rushed to take him out. Civilians with rifles in their cars started returning fire to try and prevent the asshole from shooting as the police rushed up the tower to finally take out the shooter.
Unlike the cowards of Uvalde, these men rushed to the sound of gun fire.