According to the ATF (Bureau of Alcohol, Tobacco, Firearms and Explosives), approximately 400 firearms were boosted from a United Parcel Service (UPS) facility in Memphis, Tennessee, on Sunday.

Fox 10 reports that two suspects driving a rental truck performed the robbery, absconding with an estimated 400 guns, making it one of the largest single gun thefts the ATF has ever investigated. Agents and Memphis Police officers are poring over shipping manifests and invoices to determine where the guns were shipped from and where they were going.

“We are concerned that the firearms will end up on the streets not only potentially in the Memphis area, but also across the country,” BATFE spokesman Michael Knight told Fox 10. “The criminal element knows no geographical boundary.”

An additional concern for those in the firearm industry is that a theft of this magnitude could cause shipping companies to reevaluate their firearm policies. The United States Postal Service (USPS) will not ship firearms, leaving only a handful of private companies for firearm vendors and enthusiasts to choose from. If UPS were to discontinue shipping guns, that would narrow an already tight field.

Representatives from UPS said that the company is working with law enforcement but does not comment on open investigations. The ATF has offered a $5,000 reward for information leading to an arrest and conviction. The Bureau is also asking the public to send it social media posts, photos or any other information related to the theft.