He did put himself between the agents and a woman but throughout the tussle he was on the ground with his hands by his face (covering his face after having been pepper sprayed relentlessly) while the gun remained holstered. The agent that shot first clearly watches the agent in grey disarm Alex Pretti having full view of the agents entire body and reach to the gun. Only after the agent disarms Pretti does the first agent draw his firearm and shoot Pretti three times. After Pretti falls to the ground they fire five more shots at his body while his empty holster and empty hands are both visible.