Why doesn't robinson crusoe want to shoot the savages that are running after the escaped man?

the answer would be Because the sound of the gunshot might cause the other savages to come to their rescue.

Crusoe’s thoughts turn to killing the people as perpetrators of wicked deeds and thereby saving their intended victims. While waiting every day on a hillside fully armed, Crusoe eventually changes his mind, thinking that he has no divine authority to judge humans or to kill. He also realizes that killing them might entail a full-scale invasion by the other savages.