Doctors at a health clinic in the Pentagon said one of their patients, an Army Special Forces soldier, admitted he had bought antibiotics without a prescription in the fish medication aisle of a local pet store.

The soldier, who visited the Pentagon clinic after failing to cure the infection using the pet store drugs, also told the doctors that the source of the medicines was “common knowledge” among all branches of U.S. special forces.

In addition to raising safety concerns, the report comes as doctors are expressing increasing concern about bacterial resistance to antibiotics.