Officer Zachery Curtis fired at Gregori Jackson after a traffic stop in September.
Police say Jackson attacked Curtis, then ran off into the woods.
Curtis chased him and the two struggled, then the officer shot Jackson.
An investigation by the A.G.’S Office shows Curtis reasonably believed the teenager was threatening him with deadly force and Curtis needed to use the same kind of force to protect himself.
Under the law, those two conditions must be met to justify such a shooting.