Secret Service Director: White House Intrusion 'Unacceptable'

Facing an outraged Congressional committee, Secret Service Director Julia Pierson admitted the agency's security plan "was not properly executed" -- calling the September 19 White House intrusion "unacceptable."

"I take full responsibility," Pierson said. "It will never happen again."

In a startling security lapse earlier this month, 42-year-old Omar Gonzalez, armed with a 3 inch serrated knife, scaled the north fence at the White House, stormed through the unlocked North Portico door, and barreled past an agent into the East Room just minutes after the First Family had departed the White House.

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Before he scaled the fence, Pierson revealed that two agents recognized and observed Gonzalez -- who was caught with a hatchet tucked in his waistband near the White House earlier this summer -- but did not make contact with him or report that he was present before he jumped the fence. About a month earlier, agents had interviewed and released him after officials discovered a sawed-off shotgun and several other weapons illegally stashed in his car in Virginia.

"We all are outraged within the Secret Service of how this incident came to pass," Pierson said. "It is obvious that mistakes were made."

"Protecting the White House complex is a challenge in any environment," she added. "We are never satisfied by the status quo and we are constantly reviewing our security protocols."

House Oversight and Government Reform Chairman Darrell Issa called lawmakers back to Capitol Hill to convene the rare recess hearing, saying the failure "has tested the trust of the American people in the Secret Service" to protect the president.

"Common sense tells us that there were a series of security failures, not an instance of praiseworthy restraint. Inexplicably, Omar Gonzalez breached at least five rings of security on September 19th," Issa, R-Calif., said. "The White House is supposed to be one of America's most secure facilities, and in fact, one of the world's most secure facilities. So how on Earth did it happen?"

Pierson -- brought in just 18 months ago to clean up the scandal-plagued agency -- now faces a scandal of her own. She said 16 people have been apprehended scaling the fence over the past five years, including six just this year.

"Our goal today is also clear: to determine how this happened and make sure it does not happen again," said Democrat Rep. Elijah Cummings, D-Md. "I hate to even imagine what could have happened if Gonzalez had been carrying a gun instead of a knife when he burst inside the White House. That possibility is extremely unsettling."

A "crash box" alarm that should have alerted agents of an intruder had been muted at the behest of the chief usher's office, the Washington Post reported Monday, and the agent guarding the door had no time to lock it before Gonzalez entered.

While the incident is sure to be the primary focus of the hearing, lawmakers also demanded answers about an incident the next day when an unauthorized vehicle was cleared into the White House compound, as well as a 2011 incident when a man fired several rounds at the White House while some of the president's family was inside.

Pierson reportedly requested that much of the hearing take place behind closed doors, calling a public discussion of Secret Service practices "beyond reckless." Lawmakers claimed the public deserves to know what happened, but agreed to hold a classified session immediately following today's open hearing.

ABC News' Mike Levine contributed to this report.

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