The Transportation Security Administration at Philadelphia International Airport said it intercepted a weapon at one of the security checkpoints on Thursday.

The 9mm handgun was not loaded, but was packed with five bullets accessible in an adjacent magazine, the agency said. The firearm was intercepted when the checkpoint’s X-ray unit alerted a TSA officer to the handgun in the handbag.

Police responded to the checkpoint and seized the firearm from the man, a resident of Yardley, Bucks County.

“When someone brings a loaded gun to one of our checkpoints, it’s a risk to everyone at the airport,” Gerardo Spero, TSA’s director of federal airport security, said in a news release. “Firearms pose a threat because the intent of the traveler is unknown. If you own a firearm, do not bring it to a checkpoint. If you must travel with your gun, the proper way to do so is to make sure it is unloaded, packed in a locked hard case, and taken to the airline check-in counter. The airline will ensure that it is carried in the belly of the aircraft.”

“Passengers are responsible for the contents of their hand luggage,” he added. “This individual can expect TSA to issue him a very costly federal civil penalty for his negligent actions. This is an expensive lesson to learn. Hopefully other firearms owners will learn from his mistake.”

The TSA has details on how to travel with a firearm and ammunition posted on its website.

Bringing a weapon to an airport checkpoint carries a federal civil penalty, as TSA reserves the right to issue a civil penalty to individuals who possess guns and gun parts at a checkpoint.

Civil penalties for bringing a gun into a checkpoint can run into the thousands of dollars, depending on extenuating circumstances. This applies to people with or without a concealed carry gun permit, as a concealed carry permit does not allow a firearm to be transported through a checkpoint.

The full list of civil penalties is posted online. Additionally, if a traveler with a gun is a TSA PreCheck member, that person will lose their TSA PreCheck privileges.

Not sure if an item should be packed in a carry-on bag, a checked bag, or neither? Download the free myTSA app, which has a helpful “What can I bring?” feature that allows you to enter the item to find out if it can fly. Or ask on Twitter or Facebook Messenger at @AskTSA. Travelers can submit a question by texting “Travel” to AskTSA (275-872).