This story was originally posted at 4:12 p.m. It has been updated since then.

A man with a gun that the Secret Service did not know about rode in an elevator with President Obama during his visit to the Centers for Disease Control and Prevention in Atlanta on Sept. 16.

The previously undisclosed breach, confirmed by two sources familiar with the case, raises new questions about the agency's ability to protect the president.

The incident, which took place three days before an intruder jumped a fence and sprinted inside the White House, involved a failure in Secret Service advance work to prevent an armed man from coming into close proximity with Obama while he was visiting the CDC to receive a briefing about the Ebola threat.

The threat to the president appeared minimal, but the incident alarmed agents on site and exposes a breakdown in several important Secret Service security protocols, the sources say.

The information comes the same day Secret Service Director Julia Pierson appeared before the House Oversight and Government Reform Committee and lawmakers publicly upbraided her for three hours about the Sept. 19 White House security breach, among other problems at the agency.

Lawmakers then questioned her during a session that was closed to the public Tuesday afternoon.

A source familiar with the case said Obama was in an elevator with his Secret Service security detail when a CDC security officer operating the elevator started taking photos and a video of the president with his phone and behaving unprofessionally.

Responding to the man’s behavior, one of Obama’s detail agents contacted a member of the protective intelligence team, on-site detectives who handle suspicious-activity cases, to collect the man and interview him.

When he didn’t deny taking the photos, his CDC supervisor, who was on hand for the interview, said the behavior was highly irresponsible and told him to hand over his gun, shocking the Secret Service officers who were questioning the man.

When agents ran a database check on the man, they discovered he had a criminal record, a source said.

Before the president travels anywhere, Secret Service agents make it their job to know who will have access to the president, and anyone with a gun needs special clearance and may not be allowed to carry it when the president is on site.

In addition to the Secret Service, only sworn law enforcement officers are allowed to be armed at a location where the president is visiting, the source said. Contract security officers are not allowed to be armed.

A Secret Service spokesman did not have an immediate response but said he would look into the matter and respond when he had more information.

Rep. Darrell Issa, R-Calif., chairman of the House Oversight and Government Reform Committee, said the incident is more evidence of the agency's problems.

“Given the Secret Service’s struggles to secure the White House, news of a security lapse while the president was traveling sounds like yet another symptom of systemic issues within the agency.”

Rep. Mike McCaul, R-Texas, chairman of the Homeland Security Committee, is calling for an independent top-to-bottom review of the agency and will introduce legislation creating a commission to conduct it.

“We need a comprehensive, independent assessment of the agency to ensure we have a Secret Service that can be trusted to fulfill and excel in its vital missions," McCaul said. "... The commission will recommend specific steps the Secret Service can take in order to ensure it has the best possible leadership structure, internal policies, tools, and resources to meet its mission.”