10 CFR §1049.7

1. (a)The use of deadly force is authorized only under exigent circumstances where the Protective Force Officer reasonably believes that such force is necessary to:
   1. (1)Protect himself from an imminent threat of death or from serious bodily harm;
   2. (2)Protect any person or persons in or upon the SPR from an imminent threat of death or serious bodily harm.
2. (b)If circumstances require the use of a firearm by a Protective Force Officer, the Officer shall give a verbal warning (e.g., an order to halt), if feasible. A Protective Force Officer shall not fire warning shots under any circumstances.