This video may help answer that question with a re-creation of a 1999 tragic killing of an innocent man, Amadou Diallo in New York city. This case resulted in criminal charges against the officer involved and a huge civil lawsuit. The officers were acquitted after expert testimony that included renowned firearms expert and author Massad Ayoob.
Not mentioned was the ineffective 9MM rounds that left the suspect standing after he had already been shot numerous times. In limited light officers are unable to see their bullets strike or do damage. They assume that they must have missed their target. That feeling would cause near panic conditions in anyone.