A security contractor with a gun and three prior convictions for assault and battery was allowed on an elevator with President Barack Obama during a September 16 trip to Atlanta, violating Secret Service protocols, according to three people familiar with the incident.

Obama was not told of the lapse in his security, these people said. Secret Service director, Julia Pierson, asked a top agency manager to review the matter, but did not refer it to an investigative unit that was created to review violations of protocol and standards, according to two people familiar with the handling of the case who spoke on condition of anonymity.

The incident, which took place as Obama visited the Centers for Disease Control and Prevention to discuss the U.S. response to the Ebola crisis, rattled Secret Service agents assigned to the president's protective detail.

The private contractor first aroused the agents' concerns when he was acting oddly and did not comply with their orders that he stop using a phone camera to videotape the president in the elevator, according to the people familiar with the incident.

When the elevator opened, Obama left with most of his Secret Service detail. Some agents stayed behind to question the man, and then used a national database check to learn of his criminal history.

When a supervisor from the firm providing security at the CDC approached and discovered the agents' concerns, the contractor was fired on the spot. Then the contractor agreed to turn over his gun — surprising agents, who had not realized he was armed during his encounter with Obama.

Extensive screening is supposed to keep people with either weapons or criminal histories out of arm's reach of the president. But it appears this man, possessing a gun, came within inches of the president after undergoing no such screening.

Rep. Jason Chaffetz, R-Utah, who heads a House subcommittee that oversees the Secret Service, first heard of the breakdown from a whistleblower. The Washington Post confirmed details of the event with other people familiar with the agency's review.

"You have a convicted felon within arm's reach of the president and they never did a background check," Chaffetz said. "Words aren't strong enough for the outrage I feel for the safety of the President and his family. "

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

A Secret Service official, speaking on behalf of the agency, said there is an on going investigation into the details of the incident. The official declined to provide a public comment, citing the pending review.

A White House spokesman declined to comment on the incident, or say when, or if, the president had been informed of it.

In response to a question at the hearing Tuesday, Pierson said she briefs the president "100% of the time" when his personal security has been breached. However, she said that has only happened one time this year: just days after Omar Gonzalez jumped over the White House fence September 19 and was able to burst into the mansion.

The lapse in Atlanta is the latest in a string of embarrassments for the Secret Service. Some elements of the incident were first reported Tuesday afternoon on the Washington Examiner's website.

Pierson drew criticism Tuesday from lawmakers in both parties during a combative House hearing on her agency's security lapses. The session focused on the agency's fumbled responses to a White House fence jumper last month who was able to sprint deep into the mansion and a 2011 shooting attack on the residence.

The fence breach on Sept. 19 came three days after Obama's trip to Atlanta.

The elevator incident exposed another a breakdown in Secret Service protocols designed to keep the president safe from strangers when he travels to events outside the White House.

Under a security program called the Arm's Reach Program, Secret Service advance staff run potential staff, contractors, hotel employees, invited guests and volunteers through several databases, including a national criminal information registry, and records kept by the CIA, NSA and Department of Defense, among others. Anyone who is found to have a criminal history, mental illness, or other indications of risk is barred from entry.

Local police and federal officers are not checked in the same way under the Arm's Reach Program, with the Secret Service presuming they meet the safety standards because of their employment in law enforcement. But private security contractors would typically be checked, two former agents who worked on advance planning for presidential trips said.

For nearly every trip the president takes, one or more people are barred from attending or participating in presidential events because of problems discovered in their background, the two former agents said. Most frequently, a local political party campaign volunteer who was offering to help drive staff to and from events during a visit had an assault charge in their background.

As part of the Secret Service's internal review, Pierson directed a supervising agent on the president's protective detail to stay in Atlanta after the incident to examine the breakdown.

That decision aroused suspicion on Capitol Hill. Chaffetz said he believes the director had been trying to keep another security gaffe quiet during a time that her agency and her leadership are under fire.

Former and current agents say Secret Service leaders prefer this kind of informal internal review for assessing potentially embarrasing mistakes. They say such a review rarely leads to broad reforms or consequences. These agents say it is problematic for a presidential protective detail supervisor to review how his team performed.

In an incident revealed by The Washington Post in 2013, a top manager of the president's protective detail had met a woman while drinking at a bar at the Hay Adams' hotel and left his service bullet in her room after spending the evening with her there. One of his superiors reviewed the incident and at first recommended he receive a few days of counseling. The Post report of the episode led to the agency launching a fuller investigation.