"It appears at this point that the driver was confused, not familiar with DC, and essentially got lost and followed the car in front of him," said the law enforcement source, who spoke on condition of anonymity because the investigation was continuing.
The unusual incident prompted a security lockdown at the White House. The driver, an Internal Revenue Service employee identified as Mathew Evan Goldstein, 55, was charged with unlawful entry, a misdemeanor offense.
Goldstein was released from custody on the condition that he stay away from a large area surrounding the White House, about four by six blocks in size, according to court documents.
Charging documents from the DC Superior Court said Goldstein was driving a gray Honda Civic less than five feet from the final car in a motorcade carrying the Obama daughters, Sasha and Malia, as it turned into the White House security checkpoint on Pennsylvania Avenue at 17 Street NW.
The car was too close to raise barricades to prevent the car from entering, but Secret Service officials stopped the car and detained the driver.