Which organization investigated theft of mail and assaults on postal staff?

The organization that investigates theft of mail and assaults on postal staff is the United States Postal Service (USPS). This agency has its own law enforcement division known as the United States Postal Inspection Service (USPIS). The USPIS is responsible for safeguarding the U.S. mail system and ensuring the safety of postal employees and the integrity of mail services. The Inspection Service handles various criminal activities such as mail theft, fraud, and assaults against postal workers to protect both the postal service and the public.

While the Federal Bureau of Investigation (FBI) deals with a broad range of federal crimes, including organized crime and terrorism, and the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) focuses on crimes related to firearms and explosives, as well as alcohol and tobacco control, neither of these agencies specialize in the specific concerns related to postal services. The Drug Enforcement Administration (DEA) is focused on drug-related crime investigations. Each of these agencies has its area of expertise, but the unique responsibility of the Postal Inspection Service makes the USPS the correct choice for investigating issues related to mail theft and assaults on its staff.