On any sector the FO may call stop for any a/c fire, engine failure and config warning, additionally if the FO is PF, they may call stop for a blocked runway and control difficulties.
If the FO is handling and a stop call is made the, FO WILL carry out the abort. ie. disconnect the auto thrust, close thrust levers, and ensure the a/c is braking (RTO if over 85kts, manually otherwise)
At some point during the deceleration it is the plan that the Capt will take control, usually below 80kts and attempt to turn the a/c in a sensible direction with respect to the w/v.
Once the a/c is stopped, park brake applied, the capt will then call for any relevant checklists to be carried out.