Anthony Grainger, 36, died from a single shot fired from a sub-machine gun while he sat in the front seat of an Audi in a car park.
Armed officers had swooped on the car in a ‘pre-planned’ operation in March. Two men were arrested at the scene of the shooting with a third arrested the following day.
Subsequent checks found no weapon in the vehicle. It is believed that police had ordered three men in the car to raise their hands and the shot was fired when Mr Grainger failed to do so.