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

Obama was not told about the lapse in his security, these people said. The Secret Service Director, Julia Pierson asked a top agency manager to look into 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 the condition of anonymity.

The incident, which took place when Obama visited the Centers for Disease Control and Prevention (CDC) to discuss the US 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 acted oddly and did not comply with their orders to stop using a cellphone camera to record the President in the elevator, according to the people familiar with the incident.

When the elevator doors 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 that found some prior arrests in his history turned.

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 realised that he was armed during his encounter with Obama.

Under Secret Service protocols, people with weapons, arrests or convictions for assault and related offenses or any history of mental illness are typically barred from having any access to the President. But it appears that this man, possessing a gun, came within inches of the President after undergoing no such screening.