Just three days before a knife-wielding veteran broke into the White House, Secret Service let an armed felon ride in the same elevator as President Obama.

The startling revelation that the commander-in-chief's life was compromised was revealed today, as the director of the Secret Service testified before Congress to explain the recent lapses in security.

The newest security slip-up happened on Mr Obama's September 16 trip to Atlanta, Georgia for a briefing on the Ebola crisis at the Centers for Disease Control and Prevention.

At the CDC, Mr Obama and his security detail entered an elevator when a contract security officer operating the lift started taking photos and video of the president.

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How did that happen? President Obama rode in the same elevators as a convicted felon carrying a handgun when he visited the CDC on September 16, it was revealed on Tuesday

Sources told the Washington Exmainer and Washington Post that the unnamed CDC officer ignored Secret Service orders to out the phone away, and continued to act 'oddly' and 'unprofessionally'.

When the president got out of the elevator, some of his Secret Services officers stayed behind to question the CDC employee with his supervisor, at which point they discovered he had three prior convictions for assault and battery.

When the supervisor fired the officer on the spot for acting 'highly irresponsible' she told him to hand over his gun - to the extreme shock of the Secret Service members present.

Before the president travels anywhere, Secret Service are supposed to conduct background checks on employees who work at all the venues the president will visit.

Anyone with a prior conviction is not usually allowed in the same room as the president, and only sworn law enforcement are allowed to carry guns.

The unruly security officer checked both of those boxes but somehow managed to evade Secret Service's prior detection.

Republican Representative Jason Chaffetz, of Utah, was outraged to hear about the latest lapse in security.

'You have a convicted felon within arm’s reach of the president, and they never did a background check. Words aren’t strong enough for the outrage I feel for the safety of the president and his family,' Rep Chaffestz told the Washington Post.

'His life was in danger. This country would be a different world today if he had pulled out his gun,' he added.

Secret Service Director Julia Pierson is reportedly having a top agency manager look into the matter.

Director Pierson had her plate full today when she spent three hours being grilled by a Congressional committee on the job Secret Service has been doing as of late.

Sorry: US Secret Service Director Julia Pierson apologized for a Sept. 19 White House perimeter breach by a man carrying a knife

It was also revealed in the hearing today that at least two uniformed officers noticed Army veteran Omar J Gonzales acting strange around the White House just before he jumped the fence and made it all the way to the East Room on September 19.

Gonzalez had been stopped outside the White House before, carrying a small hatchet on August 25, and the officers remembered him from that run-in.

However, Prison says they observed him 'for some time' on September 19, but did not intervene.

'It is clear that our security plan was not executed properly,' Pierson told lawmakers. 'I take full responsibility; what happened is unacceptable and it will never happen again.'