The incident, which took place when 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 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 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 turned up his criminal history.