Amid growing calls in the Congress for new leadership, Secret Service Director Julia Pierson submitted her resignation on Wednesday, as the Obama Administration approved the creation of an outside panel of experts to look at the work of the Secret Service.

"Director Pierson offered her resignation today because she believe it was in the best interests of the agency to which she has dedicated her career," said White House spokesman Josh Earnest.

In a late afternoon briefing, Earnest surprised reporters by saying that the White House had been blindsided by a story about a security breach during a trip to Atlanta in mid-September by President Obama.

"The White House first learned of that incident yesterday afternoon, shortly before it was reported," said Earnest.

It was a stunning acknowledgement by the White House, maybe indicating that the news of a contract security officer - armed with a gun and featuring past felony convictions - had been the last straw for the Secret Service chief.

As for a replacement, lawmakers in both parties said there needs to be more than just a new person in charge of the Secret Service.

"They need a cultural change," said Rep. David Scott (D-GA). "These recent incidents are disturbing."

The White House would not say if Pierson had been forced out; she will be temporarily replaced by a former Secret Service agent who served on Presidential protective details.