It is a crime to kill or attempt to kill a federal agent who is engaged in the performance of his official duties. This law is found in 18 USC Section 1114.

The “performance” prong of this statute does not have a specific definition. Whether an officer is “performing” his duty is generally determined by evaluating whether he is acting within the scope of his employment rather than on a personal frolic.

For example, in United States v. Stephenson, the court determined that an FBI officer was performing within the scope of her employment when she attempted to fight off the defendant who tried to steal her purse. The court reasoned that because her purse contained her service revolver and identification, she was within the scope of her employment.