A passenger who flew out of Hartsfield-Jackson International Airport in Atlanta Nov. 5 said he brought a loaded gun through security and boarded a plane to Chicago without ever being detained.

Blake Alford, a retired truck driver, claimed he made an "honest mistake" when he accidentally left a loaded semiautomatic pistol in his backpack when he flew on the Southwest Airlines flight, reported the Las Vegas Review-Journal. He said he put his backpack through the x-ray machine at the airport, but security didn't notice the firearm.

He realized he still had the gun loaded once arriving in Chicago, prompting him to unload the pistol and put it into a checked bag for his return trip. Once back in Atlanta, knowing that terrorists are still active across the globe, he notified airport officials to alert them about their oversight.

"People need to know TSA needs to tighten up," said Alford, according to CBS' Atlanta affiliate WGCL-TV. "If they'll take toothpaste, they'll make people get out of wheelchairs, they'll make me take off my belt buckle and my shoes, how did my gun go through?"

The Transportation Security Administration issued a statement saying it is investigating the matter "to determine what occurred and what steps, if any, need to be taken to ensure that security protocols are executed appropriately."

"If we find that standard procedures were not adhered to, we will retrain employees as necessary to ensure compliance with standard operating procedures. When our employees fail to meet standards, we hold them appropriately accountable," declared the agency, according to Atlanta Journal Constitution.

This incident raises concerns about the level of security at U.S. airports after TSA Administrator Peter Neffenger told a congressional panel in July that his top priority would be to strengthen security at airport checkpoints, following the release of a report that revealed that TSA agents failed to detect banned weapons 67 out of 70 times.

The TSA reports having discovered 2,447 firearms in cary-on bags so far in 2015.

Atlanta Mayor Kasim Reed visited Hartsfield-Jackson airport to receive an update on security earlier today.