Officials said the inmate was restrained and the firearm was seized. Federal officials have launched an investigation.
The Bureau of Prisons has been plagued by chronic mismanagement, misconduct and a severe staffing crisis. A new director was brought on earlier this year as Justice Department officials attempt to reform the agency.
Federal prison camps were originally designed with low security to make operations easier and to allow inmates tasked with performing work at the prison, like landscaping and maintenance, to avoid repeatedly checking in and out of a main prison facility. But the lax security opened a gateway for contraband, such as drugs, cellphones and weapons.