The officer who shot an unarmed black man during a South Carolina traffic stop says he fired in self-defense after a struggle over his stun gun.

Officer Michael Slager was charged with murder and fired after a video challenged his version. But the case points to a paradox in policing: Stun guns were meant to help police avoid using lethal force, but sometimes they become part of the problem.

The Associated Press found a half-dozen other fatal police shootings of black men involving stun guns recently.

The maker of Taser says its stun guns are "safe, effective and accountable." But a policing expert tells AP that stun guns can give officers a false sense of control, and civil rights advocates say police need to focus instead on de-escalating violent situations.