Gao Yang's gunstock was hit by a bullet at its very edge, leaving a nick.
It didn't require much deduction to know that the old Tuareg man hadn't made a mistake in direction nor had he chased in the wrong direction; he had set a trap for Gao Yang.
Gao Yang had set a trap for the Old Fox, and the Old Fox had turned it around on him.
Putting himself in his enemy's shoes, Gao Yang still greatly admired the Old Fox's technique.
By then, Gao Yang was sure that after seeing the body and ruling out Mines and checking the tracks, the Old Fox knew he was hiding nearby. Although he had excellent camouflage and precise gunmanship, if the Old Fox couldn't be sure of his position and started searching immediately, Gao Yang could have left quietly, but more likely, he would have seized the opportunity to fire a shot.