In the United States, a special agent is a detective or investigator who investigates suspected s of federal, state or local laws. Special agents may also carry firearms and make arrests. Special agents work for many different law enforcement agencies. In some agencies, only special agents may carry firearms. An example is special agents in the Internal Revenue Service. To become special agents most applicants must pass written and physical examinations. In the FBI, like many agencies, applicants must go through a background check.