(CNN) - It seems at this point to be an honest mistake.
That's what a source tells CNN's Michelle Kosinski about Tuesday's security breach that resulted in a White House lockdown.
A Secret Service source explains that Mathew Goldstein, 55, got caught up in traffic-circle confusion during the heavy afternoon rush in downtown D.C.
Unfamiliar with the traffic pattern, he apparently panicked and made a sharp right turn that put him immediately behind a group of cars, which turned out to be a White House motorcade.
The IRS computer worker from Maryland drove along behind those vehicles carrying President Barack Obama's two daughters and rolled right through a perimeter barricade on Pennsylvania Avenue.
But how did the Secret Service let him through?
The guards apparently didn't have time to raise the bollards fast enough to shut out Goldstein's gray Honda Civic, which was only about five feet behind the closest vehicle, charging papers said.
But he was stopped immediately and then was arrested.
However, the source said it appears to be an honest error on the driver's part.
The breach prompted a temporary lockdown of the White House complex where Obama was meeting with Secretary of State John Kerry.
Goldstein pleaded not guilty on Wednesday to a misdemeanor charge of unauthorized entry. He was released on his own recognizance, pending a hearing on May 21.
The judge ordered he stay away from the White House and its grounds.
CNN Supreme Court Producer Bill Mears contributed to this report.