El Tejon said, "
Fine shooting especially after the first shot.
I assume that statement was in regard to the fact that people on the ground radically changed their normal behavior and fled in all directions. Actually, many people were shot before it was determined as to what was going on and where the shots originated. Additionally, Whitman fired in several directions. People off in the distance and on opposite sides of the tower were still surprised well into the rampage. Distance from the tower and the tower and administrative building served to block information flow to side as to what was happening on the other side.
I am not sure how effective the hunter's (with hunting rifles) shooting was on the situation. Given the wall around the tower's catwalk and the angle of the shots being made from the ground, Whitman presented only a minimal target to hit and he apparently knew it. The folks on the ground would shoot toward the top of the tower whenever they saw his rifle over the catwalk wall. They were not so much able to shoot at him, just toward his immediate vicinity. Whitman managed to coninue hitting victims on the ground long after the hunters tried to do their part to stop him.
Not only did the wall help protect him, but when fire was directed toward him, he switched to shooting out through the rain gutter channels in the wall. This made him virtually impossible to hit as the gutters were only a few inches in size.
To be able to hit Whitman, the shooters one the ground would have needed to exceed Whitman's abilities, which they did not. Whitman hit folks who were only slightly exposed (between 2 pillars six inches apart, as head peeked around corners, and even those way off in the distance [furthest hit was 500 yards and that was after his location was under heavy fire.
For more information, see
http://www.crimelibrary.com/serial/whitman/