A South Carolina police officer charged with murder after shooting an unarmed man in the back had a prior complaint made against him about using force.

The police are re-investigating Michael Slager’s use of a stun gun on Mario Givens in 2013.

Mr Slager was charged with the murder of Walter Scott, 50, after a video of Saturday’s fatal shooting emerged.

The man who shot the video says he saw the two men having a scuffle on the ground before Mr Scott ran away.

Mr Slager was fired by the North Charleston police department following the murder charge.

He has been held without bail and faces up to life in prison if convicted of murder.