The gunman who opened fire Friday in a deadly attack at the airport in Fort Lauderdale, Fla., pulled his weapon out from an unlikely place in this post-9/11 era of tightened airport security and pat-downs by the Transportation Security Administration — his checked luggage.

The shooting unfolded in a crowded baggage claim area of the airport, after the gunman’s flight had arrived in Fort Lauderdale and he had retrieved his checked bags, officials said. The suspect, Esteban Santiago, was accused of killing at least five people and wounding at least eight others, the authorities said.

According to the T.S.A., passengers at the nation’s airports are allowed to transport unloaded guns in their checked baggage. The firearms must be kept in a locked “hard-sided” container, and gun owners must declare firearms and any ammunition to airline representatives when checking the bags at ticket counters, according to the agency’s firearm regulations. Guns, real ones as well as replicas and toys, are allowed to be transported only in checked baggage, not in carry-on luggage. The same is true for clips, firing pins and other firearm parts.