Wrong weapon drawn. Never pull a weapon you arent prepared to use. His saving grace came when the other officers arrived. Until that point, the officer was not in control of that situation.
Not saying he should have shot and killed him. Saying he shouldnt have drawn a gun if he wasnt ready and prepared to use it. As soon as he fell he was vulnerable. Had the other two cars not arrived at that point the suspect would have been on top of him grappling with him for a loaded and charged weapon.